Tissue responses against Cladosporium trichoides and its parasitic forms in congenitally athymic nude mice and their heterozygous littermates

The tissue responses against Cladosporium trichoides and its parasitic forms were studied using nude (nu/nu) mice and their heterozygous (nu/+) littermates of BALB/c background.1.0,0.1 and 0.01% cell suspensions were prepared from a culture broth which had been inoculated with the C. trichoides and cultured with reciprocal shaking at 27 ° C for 7 days. Sixty nu/nu or 60 nu/+ mice were divided into three groups consisting of 20 each which was allotted to one of the three cell suspensions. Each mouse was inoculated intravenously with 0.1 ml of either the cell suspensions. Two mice from each of the six groups were sacrificed at adequate intervals until 30 days after inoculation and histopathologic sections stained with H & E or by PAS were prepared from their visceral organs.There were no characteristic findings in the nu/nu and nu/+ mice inoculated with the 0.01% cell suspension. When inoculated with the 1.0% cell suspension, the brain was the favorite target organ in both groups of mice and the kidney was the second. When inoculated with the 0.1% cell suspension, brain lesions were observed only in the nu/nu mice. The susceptibility of the nu/nu mice was higher than that of the nu/+ mice.The parasitic forms in the brain of the nu/nu and nu/+ mice were slender septate true hyphae with or without polymorphonuclear leucocyte infiltrate, while in the liver, spleen and lung of both groups of mice the parasitic forms were short thick hyphae, moniliform hyphae, chlamydospores or round cells (sclerotic cells). Many giant cells containing fungal elements appeared in the liver of the nu/nu mice.     

Granuloma formation and killing functions of granuloma in congenitally athymic nude mice infected with Blastomyces dermatitidis and Paracoccidioides brasiliensis

We did this experiment to clarify the mechanism of granuloma formation and the killing functions of granuloma in nude mice against Blastomyces dermatitidis and Paracoccidioides brasiliensis infections. B. dermatitidis A-295 and P. brasiliensis B-1183 were the cultures used. Congenitally athymic nude (nu/ nu) mice and their heterozygous (nu/ +) littermates of BALB/ c background were the test animals. From culture A-295, 0.1% and 1% cell suspensions (wet weight) were prepared and from culture B-1183 0.2% and 2% cells suspensions were prepared. Ten nu/ + and 10 nu/ nu mice were allotted to each of four cell suspensions. For experimental blastomycosis each mouse was inoculated intravenously with 0.2 ml of the cell suspension of A-295 and for experimental paracoccidioidomycosis, with 0.15 ml of the cell suspension of B-1183. Two mice from each of the four groups were killed at 5, 8, 12, 18 and 25 days after inoculation, and histopathologic sections, stained with H&E or by PAS, were prepared from various internal organs.In the nu/ nu mice inoculated with B. dermatitidis A-295 granuloma was formed in the brain tissue after the 12th day. However, mononuclear cells, which formed the granuloma, did not kill the fungal cells, and the fungal cells continued to multiply in the granuloma. On the other hand, in the heart, kidney and fat tissue, their histopathological findings after the 18th day were clumps of fungal cells with slight cell reactions. In these organs the exertion of cell-mediated immunity was necessary for granuloma formation against the fungal infection.In the nu/ nu mice infected with P. brasiliensis B-1183, granuloma appeared in the brain and kidney after the 18th day and fungal cells continued to multiply within the granuloma as well as in those inoculated with culture A-295.These results show that the exertion of cell-mediated immunity plays an important role as the defense mechanisms of hosts against these fungal infections. However, PMNs also play an important role in the mouse's defense mechanisms against these fungal infections.We assume that the defense mechanisms of immunocompetent mice against B. dermatitidis or P. brasiliensis infection consist chiefly of two steps: in the first step phagocytosis by PMNs occurs and in the second step cell-mediated immunity enters into play.     

Experimental histoplasmosis capsulati in athymic nude mice

Granuloma formation in nude (nu/nu) mice and their heterozygous littermates (nu/+ mice) against Histoplasma capsulatum var. capsulatum infection was studied.A culture of H. capsulatum var. capsulatum, isolated from a granuloma in the nasal cavity of a Japanese patient, was used in this experiment. Sixteen specific-pathogen-free male nu/nu and 32 nu/+ mice were used in this study.The nu/+ mice were divided into two groups. Sixteen nu/+ mice in one group and 16 nu/nu mice were inoculated intraperitoneally with 10⁶ yeast cells of the fungus, those in the other group of nu/+ mice were inoculated intravenously with the same number of the yeast cells. Two mice out of each group were sacrificed 2, 3, 7, 11, 14, 18, 25 and 30 days after inoculation, and each of their organs was examined histopathologically. In addition, pieces of these tissues were cultured on Sabouraud's dextrose agar slants.In the nu/+ mice inoculated intraperitoneally, although the fungus was recovered from the spleen, kidney and lymph nodes during the initial course of the infection, lesions were not detected in their histopathological sections. In the nu/+ mice inoculated intravenously, colonies were recovered from all of the organs examined, other than the brain and thymus, 7 days after inoculation.Histopathologically, a few microfoci consisting chiefly of mononuclear cells with or without yeast cells were found in the liver sections 4 days after inoculation. Seven and 11 days after inoculation the number of lesions had increased. They had large accumulations of mononuclear cells. From day 14 on, almost all of the yeast cells had lost most of their staining affinity or were destroyed in the granuloma. From day 25 on, the granulomatous lesions changed gradually to fibrous tissue.In the nu/nu mice the fungus was readily recovered from the spleen, liver, kidney and lymph nodes. Histopathologically, a few microfoci consisting of mononuclear cells were present in the liver sections 4 days after inoculation. That is to say, during the initial course of infection granulomas were formed. In the liver, from day 7 on, the lesions were large and their number increased. However, there was a definite difference between the nu/nu and nu/+ mice. In the former, the yeast cells were not killed, and they continued to multiply within the granulomas. These granulomas were never transformed into fibrous tissue.     

Histopathological studies on experimental Cryptococcosis in nude mice

Cryptococcosis in nude (nu/nu) mice was examined histopathologically. In addition, effects of carrageenan and lymph node cell transfer againstCryptococcus infection were investigated. As controls, heterozygous littermates (nu/+mice) and mice of strain ddy (ddy mice) were employed.Each mouse was inoculated intravenously with 10⁵ yeast cells ofCryptococcus neoformans suspended in 0.2 ml phosphate-buffered saline. Two mice out of each group were sacrificed at appropriate intervals up to 25 days after inoculation and histopathological sections were prepared from them. They were stained with H & E and by PAS method. Histopathological characterristic in the brain was cyst formation with no cellular response. The brain was more severely in the nu/nu mice than in either the nu/+ or ddy mice. In the liver, there was a major difference in histopathological findings between the nu/nu and either of the other groups of mouse. In the nu/nu mice, cyst formation with no cellular response was induced, and on the contrary granuloma formation in the nu/+ and ddy mice. However, the granuloma formation was inhibited in the livers of the nu/+ and ddy mice by administration of carrageenan, and induced in the nu/nu mice by cell transfer. In the spleen and lymph nodes, lesions were severer in nu/nu mice than in either the nu/+ or ddy mice.These results suggested that the fungus' invasiveness of mice was strongly influenced by T-cell dependent mechanism.     

Defensive role of granuloma againstSporothrix schenckii infection

The defensive role of granuloma againstSporothrix schenckii infection was studied histopathologically using nude(nu/ nu) and their heterozygous(nu/+) littermates.Three strains ofS. schenckii (Sp.-1, Sp-17 and Sp-56) were used in this experiment. Each mouse was inoculated into a tail vein with 10⁶ yeast cells of the Sp-1, Sp-17 or Sp-56. The mice were sacrificed at adequate intervals until the 30th day and histopathological sections were prepared from various organs.The numbers of lesions and yeast cells were counted using the liver sections. Furthermore, an experiment of lymph node cell transfer and immunological examinations were carried out.As results the susceptibility of mice to three strains were conspicuously different from each other. The Sp-1 showed the strongest pathogenicity and the Sp-56, the weakest. The susceptibility of the nu/ nu mice inoculated with the Sp-1 was much higher than that of the nu/+ mice and the difference was due to the killing functions of granuloma. Even though about two days' delay was observed in the granuloma formation in the nu/ nu mice in comparison with that in the nu/+ mice, these granulomata could not be distinguished from those of the nu/+ mice. However, functionally there was a definite difference between the granulomata formed in the nu/+ and nu/nu mice. Mononuclear cells forming the granulomata in the nu/ nu mice did not have the ability to kill the yeast cells they had engulfed. Cooperation with T-lymphocytes was necessary for the killing of the yeast cells. A significant response of MIF developed in the immunocompetent mice 11 days after inoculation of the Sp-56, and that day nearly coincided with the day when yeast cells of the Sp-1 began to be destroyed in the granulomata. It was also confirmed by the experiment of lymph node cell transfer that T-cell functions were indispensable for the killing of the yeast cells by mononuclear cells.From these results the authors hypothesize that the mononuclear cells activated with T-lymphocytes could play a leading role as the defense mechanism of mice againstS. schenckii infection.     

Mycoplasma pulmonis Arthritis in Congenitally Athymic (Nude) Mice

Histopathological examinations were performed on arthritic joints and other organs of strain BALB/cA nu/nu and nu/+ mice intravenously injected with Mycoplasma pulmonis strain m53. In both groups of mice suffering from polyarthritis, acute inflammatory lesions with infiltration of polymorphonuclear leukocytes in the synovia and periarticular tissues were observed one to two weeks after injection. In nu/nu mice, the acute inflammation appeared repeatedly up to 20 weeks after inoculation, when the experiment was terminated, and furthermore, extensive synovial and periarticular necrosis were characteristically present after the 4th week. Only a small number of lymphocytes and plasma cells were in the lesions. In nu/+ mice, after the early acute inflammation of arthritis, relapses of the infiltration of polymorphonuclear leukocytes were also observed in some mice in and after the 10th week. In addition, infiltration of lymphocytes and plasma cells was substantial after the 15th week. Focal necrosis was sometimes found in the liver of nu/nu mice. Perivascular infiltration of small lymphocytes and plasma cells was found in the lungs, liver and kidney of nu/+ mice in and after the 15th week. Repair mechanisms of injured articular tissues in nu/nu mice were histopathologically poor, while those in nu/+ mice seemed to be progressive and quite similar to those reported by many investigators for mice with the thymus intact. The histopathological differences are discussed in respect to the thymus-dependent immune responses.     

Defensive role of granuloma againstSporothrix schenckii infection

The defensive role of granuloma againstSporothrix schenckii infection was studied histopathologically using nude(nu/nu) and their heterozygous(nu/+) littermates. Three strains ofS. schenckii (Sp.-1, Sp-17 and Sp-56) were used in this experiment. Each mouse was inoculated into a tail vein with 10⁶ yeast cells of the Sp-1, Sp-17 or Sp-56. The mice were sacrificed at adequate intervals until the 30th day and histopathological sections were prepared from various organs. The numbers of lesions and yeast cells were counted using the liver sections. Furthermore, an experiment of lymph node cell transfer and immunological examinations were carried out. As results the susceptibility of mice to three strains were conspicuously different from each other. The Sp-1 showed the strongest pathogenicity and the Sp-56, the weakest. The susceptibility of the nu/nu mice inoculated with the Sp-1 was much higher than that of the nu/+ mice and the difference was due to the killing functions of granuloma. Even though about two days’ delay was observed in the granuloma formation in the nu/nu mice in comparison with that in the nu/+ mice, these granulomata could not be distinguished from those of the nu/+ mice. However, functionally there was a definite difference between the granulomata formed in the nu/+ and nu/nu mice. Mononuclear cells forming the granulomata in the nu/nu mice did not have the ability to kill the yeast cells they had engulfed. Cooperation with T-lymphocytes was necessary for the killing of the yeast cells. A significant response of MIF developed in the immunocompetent mice 11 days after inoculation of the Sp-56, and that day nearly coincided with the day when yeast cells of the Sp-1 began to be destroyed in the granulomata. It was also confirmed by the experiment of lymph node cell transfer that T-cell functions were indispensable for the killing of the yeast cells by mononuclear cells. From these results the authors hypothesize that the mononuclear cells activated with T-lymphocytes could play a leading role as the defense mechanism of mice againstS. schenckii infection.     

Studies on defense mechanisms against Candida albicans infection in congenitally athymicnude (nu/nu) mice

The defense mechanisms against Candida albicans infection were studied by using a mouse thigh lesion model in congenitally athymic nude (nu/nu) mice and their normal littermates (nu/+). Nu/nu mice were more resistant to C. albicans infection than nu/+ mice judging from the course of the thigh lesion, the results of CFUs (colony-forming units) of C. albicans in the lesion, and histopathological observations. Histopathological and serological studies revealed that granulocytic cellular infiltration was predominant, and there were few indications of development of cell-mediated immunity to protect Candida infection in Candida-infected nu/nu and nu/+ mice. These results confirmed that lower susceptibility of nu/nu mice to C. albicans infection as compared with nu/ + mice was due to accelerated non-specific defense mechanisms in nu/nu mice, and that cell-mediated or humoral immunity played a minor role in the defense against Candida infection in this experimental model.Furthermore, treatment with high titer of rabbit anti-C. albicans serum was effective to control the number of Candida cells in thigh lesions of BALB/c mice.Above experimental results seem to clearly indicate the great variability of defense manifestation according to the experimental model exployed.     

Antigen-induced acceleration of shedding and replacement of B cell antigen receptors requires mature T cells

To determine which early and intermediate events in the response of antigen-binding B cells to a T-dependent antigen (sheep erythrocytes [SRC]) require T help, the antigen-induced changes in receptor turnover and surface IgD loss in BALB/c athymic nu/nu mice were compared with that of nu/+ littermates and +/+ BALB/c mice. Nonimmune SRC antigen-binding spleen B cells (ABC) from +/+, nu/+, and nu/nu BALB/c mice coexpressed IgM and IgD, and 85 to 95% retained receptors well when incubated for 2.5 hr in 100 micrograms/ml cycloheximide (which prevents receptor replacement). Also they were able to regain their ability to bind antigen by 18 hr after pronase treatment, but not by 2 hr. However, 5 days after in vivo immunization, 1) the proportion of ABC expressing surface IgD declined from around 90% to less than 50% in +/+ mice and nu/+ mice but not in nu/nu mice; 2) substantial recovery of antigen-binding occurred by 2 hr after pronase treatment in +/+ and nu/+ ABC but not in nu/nu ABC; and 3) when spleen cells were incubated in cycloheximide, uncompensated receptor shedding reduced +/+ and nu/+ ABC by around 80% but produced only about a 10% reduction in nu/nu ABC. Thus, although the ABC in nonimmune nu/nu mice appeared normal with respect to their surface Ig turnover and expression, they failed to undergo the normal antigen-induced loss of IgD or acceleration of surface Ig shedding and replacement, suggesting that these intermediate activation events require interaction with mature T cells. To determine whether this interaction had to occur during B cell development, during the development of the immune response, or during receptor shedding or replacement itself, cell transfer experiments were carried our wherein nu/+ T cells were transferred i.v. to nu/nu littermates 1 day before immunization with SRC. In the transfer recipients, pronase-treated day 5 ABC were then able to replace and shed their receptors at the accelerated rate, like ABC from +/+ and nu/+ mice. In contrast, the co-incubation of 5-day immune nu/+ T cells with nu/nu B cells did not alter the rate of shedding or replacement.     

Induction of granuloma-dependent angiotensin-converting enzyme and eosinophil chemotactic factor in the skin of athymic nude mice

Activities of angiotensin-converting enzyme (ACE), other proteinases, and eosinophil chemotactic factor (ECF-G) are known to be elevated in hepatic hypersensitivity granulomas of thymus intact (nu/+) mice after Schistosoma mansoni infection. The enzyme activities also increase, but to a lesser degree in hepatic granulomas of athymic nude (nu/nu) mice, and ECF-G is not detectable. In this study isolated hepatic granulomas from nu/+ mice were grafted into the skin of uninfected nu/nu mice, and changes in those cellular functions were determined to examine whether the newly formed granulomas by recipient nu/nu cells acquire the functional activities as well as the histological appearance of nu/+ granulomas. ACE and ECF-G rapidly disappeared from grafted sites during the first 5 days, corresponding to loss of nu/+ cells from the graft. Reduction in activities of arylsulfatases, lysozyme, and acid phosphatase also occurred, but to a lesser extent. Recovery of ACE and ECF-G activities to the levels seen in nu/+ hepatic granulomas was observed by 14 days after grafting when nu/nu cells had accumulated in the grafts and formed new granulomas. Other enzymes increased to approximately half the levels seen in grafted donor granulomas. Circulating eosinophilia also increased. The findings indicate that nu/nu cells that accumulated in the skin grafts not only morphologically mimicked nu/+ type granulomas but also demonstrated nu/+ levels of cellular function. Analysis of skin granulomas developing in nu/+ mice after grafting of nu/+ hepatic granulomas showed the similar histology and enzymatic changes, whereas the skin sites inoculated with purified schistosome eggs alone caused neither significant histological changes nor elevation of ACE activity.     

Macrophages of athymic nude mice: Fc receptors, C receptors, phagocytic and pinocytic activities

Expression of Fc receptors (FcR) for IgG1, IgG2A, IgG2B, IgM, IgA and IgE, binding of C3 and C5 complement components and phagocytic and pinocytic activities were determined in peritoneal and omental macrophages of nu/nu, nu/+ and +/+ Balb/c mice. nu/nu mice showed a higher proportion of FcR and complement receptor-bearing peritoneal macrophages along with a significantly higher phagocytic activity of peritoneal macrophages both in vitro and in vivo. Tests of pinocytic activity in these cells and phagocytic activity in omental phagocytes yielded similar results. We conclude that athymic mice compensate their immune defects by a higher phagocytic activity of their professional phagocytes and a higher expression of receptors mediating this process.     

Effect of immune heterozygous spleen cell transfer on resistance to mouse hepatitis virus infection in nude mice

The role of cell mediated immune response to mouse hepatitis virus (MHV) infection in mice was studied by transferring spleen cells from immune heterozygous littermates (nu/+). A suppressive effect on viral growth was seen in infected nude (nu/nu) mice, whereas immune nu/+ serum transfer had no effect. The protective effect of immune nu/+ spleen cells was significantly reduced by treatment with anti-theta serum plus complement but not with anti-Ig serum. In infected nu/nu mice which received transfers of immune nu/+ cells, neutralizing antibody appeared although the titer was not high enough to protect nu/nu mice from fatal infection. Histopathologically, lymphocyte infiltration in hepatic lesions was evident in infected nu/nu mice with nu/+ cell transfer, while it was slight without nu/+ cell transfer.     

Immunologic abnormality in NZB/NZW F1 mice. Thymus-independent occurrence of B cell abnormality and requirement for T cells in the development of autoimmune disease, as evidenced by an analysis of the athymic nude individuals

Both NZB nu/+ and NZW nu/+ mice were microbially clean by cesarean section. The (NZB x NZW)F1 hybrid (NZB/W) nu/nu mice and nu/+ littermates were then generated by mating of NZB nu/+ with NZW nu/+mice under specific pathogen-free conditions. The female NZB/W F1 nu/nu mice did not develop autoimmune kidney disease, whereas all of nu/+ female littermates mice exhibited proteinuria and died of renal failure with a 50% survival time of 35 wk. Namely, nude mice had no signs of proteinuria up to the time of their death caused by other diseases rather than glomerulonephritis, and their mean survival time was greater than 45 wk. Nude mice had also no anti-ssDNA antibody in their serum. However, splenic B cells of NZB/W nude mice exhibited hyper-responsiveness to both LPS and B151-TRF2, a T cell-derived polyclonal B cell-stimulation factor, and produced large numbers of Ig-secreting cells and anti-TNP plaque-forming cells as well as anti-ssDNA antibody comparable to the nu/+ littermate mice. Interestingly, thymus-engrafted NZB/W nude mice developed autoimmune disease exemplified by the induction of anti-ssDNA antibody and proteinuria at approximately the same time as their nu/+ littermates. These results indicate that the B cell hyper-responsiveness found in NZB/W mice is apparently determined by the T cell-independent process, and T cells are obligatorily required for the development of autoimmune disease in NZB/W mice.     

Polyclonal Antibody Production in Murine Spleen Cells Induced by Staphylococcus

Polyclonal plaque-forming cell (PFC) responses in murine spleen cells induced by Staphylococcus aureus and S. epidermidis were studied. Injection of Balb/c mice with S. aureus strain 248βH resulted in the generation of anti-trinitrophenyl (TNP) and anti-sheep red blood cell PFC in their spleens. Cultures of Balb/c spleen cells in the presence of S. aureus 248βH, Cowan I, or a protein A-deficient mutant yielded many anti-TNP PFC. The larger the number of organisms that were added to the cultures, the better was the PFC response. Both living and killed organisms, were capable of inducing the response, but an excess of living 248βH organisms in the cultures abrogated the response. All of the organisms (12 strains of S. aureus and 11 strains of S. epidermidis) freshly isolated from patients had the ability to induce the polyclonal PFC response in cell cultures. These organisms stimulated cultured C3H/HeJ mouse spleen cells, which were unresponsive to bacterial lipopolysaccharide (LPS). Cultured cells from the spleens of athymic nu/nu mice also responded to these organisms, and the number of PFC in nu/nu cell cultures was always greater than that in nu/+ cells prepared from a haired litter mate. Moreover, the responses of nu/nu spleen cell cultures to which nylon wool column-filtered splenic nu/+ T cells were added were lower than expected. These findings suggest that the polyclonal PFC response to staphylococci is thymus independent, but that the magnitude of the response is regulated by mature T cells. Cultures of macrophage-depleted spleen cells responded to the organisms to an extent similar to that of the control. The 248βH organisms were less capable of stimulating spleen cells of 2-week-old mice (i.e., early maturing B cells) than LPS. However, spleen cells from adult (7-week-old) and aged (9-month-old) mice responded well to both the organisms and LPS. Previous sensitization with the organisms in vivo did not affect any polyclonal responses of spleen cells in vitro to either the organisms or LPS. The role of staphylococcal protein A in the polyclonal PFC response to staphylococci is discussed.     

Characterization of mononuclear phagocytes in schistosomal egg granulomas of athymic mice

Macrophages from schistosomal egg granulomas of athymic mice (nu/nu GM) and their euthymic littermates (nu/+ GM) were analyzed phenotypically for the expression of antigens encoded by the I-A subregion of the major histocompatibility complex and for their ability to perform as antigen-presenting cells. Only 11 to 15% of nu/nu GM expressed I-A antigens as compared to 61.5 to 75% of nu/+ GM. Although both populations of cells appeared to be equally effective as antigen-presenting cells appropriately sensitized lymphocytes in the presence of specific antigens--soluble schistosomal egg antigen (SEA) and human gamma-globulin (HGG)--only nu/nu GM, but not nu/+ GM, were found to stimulate I-A-restricted proliferation of schistosome-sensitized T cell populations in the absence of SEA added in vitro. Furthermore, nu/nu GM but not nu/+ GM were shown to exhibit significant proliferative capacity in vitro, but this phenomenon could not account for the observed difference in SEA-independent T cell stimulation. Finally, culture supernatants from nu/nu GM displayed significant thymocyte-stimulating activity, consistent with interleukin 1, which was not observed in nu/+ GM. These findings point to significant differences between nu/nu GM and nu/+ GM, which may be part of an adaptive mechanism of granulomatous reactivity in the absence of a competent T cell system.     

Immune response in mice infected with Candida albicans in the mycelial form

The effect of the infection with the mycelial form of a Candida albicans strain (Mycology Dept.) upon the immune system in mice was studied.BALB/c mice were infected intraperitoneally in a single dose of a 3×10⁶, 6×10⁶ and 12×10⁶ cell suspension of the strain.Macrophages's activity was studied the days 7,14,21,28, 35, and 42 after inoculation, by the following assays: phagocytosis in vitro, mononucleated phagocytic system by the colloidal carbon clearance technique, the lymphocyte's activity by the direct plaque forming cells technique (PFC) and delayed hypersensitivity (DTH).Infection with the mycelial form did not affect the peritoneal macrophage's phagocytic ability, neither modified the delayed hypersensitivity to sheep red blood cells (SRBC). However, a slight and transient depression of the lymphocyte stimulation was found. Suppression of PFC to SRBC was high when a 12×10⁶ cell suspension was used in contrast to the infection with blastospores.These results suggest that systemic infection by Candida albicans in its mycelial form do not induce a non specific immunosuppression.     

Cells with natural killer activity in the cerebrospinal fluid of normal mice and athymic nude mice with acute Sindbis virus encephalitis

Sindbis virus causes an acute, nonfatal inflammatory encephalitis in weanling BALB/c mice. Mononuclear inflammatory cells are present in the cerebrospinal fluid (CSF) as well as in the parenchyma of the brain. Both aspects of this inflammatory response were eliminated by treatment with cyclophosphamide. Athymic nude (nu/nu) mice developed no inflammation in the brain, but did develop a CSF pleocytosis that peaked on day 2 after infection. The time course of the appearance of cells in the CSF was earlier in nu/nu mice than their heterozygote (nu/+) littermates. The pleocytosis in nu/nu mice reached a peak on day 2, whereas in nu/+ mice the peak was on day 4, as it is in normal BALB/c mice. To determine whether some of the CSF cells in nu/nu mice may be natural killer (NK) cells, NK activity was measured in a 4-hr assay by using a YAC-1 target cell. NK cell activity in the spleen and peripheral blood was induced by infection with Sindbis virus in nu/nu mice with a similar time course to that of nu/+ mice (peak 1 day after infection). CSF from nu/nu mice had NK activity present 2 days after infection that was greater than that present in either the peripheral blood or spleen. BALB/c and nu/+ mice had insufficient cells present for assay at day 2, but BALB/c mice had NK activity present in the CSF 3 and 5 days after infection that exceeded that in the peripheral blood or spleen. Brain interferon was detectable on day 1 in nu/nu mice, but not until day 2 in nu/+ mice even though the amounts of brain virus were the same in the two groups at all time points. It is concluded that cells with NK activity contribute to the CSF pleocytosis induced by acute Sindbis virus encephalitis.     

Regional variations in the distributions of small intestinal intraepithelial lymphocytes (IELs) in BALB/c +/+, nu/+, and nu/nu mice

Regional variations in intraepithelial lymphocytes (IELs) in the small intestine were examined in BALB/c +/+, nu/+, and nu/nu mice. The small intestine was obtained from 11- to 12-week-old mice and divided equally into three (proximal, middle, and distal) parts. The IELs were isolated from each part of the intestine, and the total numbers of IELs in nu/+ and nu/nu mice were about a fifth of those in +/+ mice. Regional variations in the distribution of the IEL alphabeta, but not the gammadelta T-cell subset were found by use of flow cytometry in +/+ and nu/+ mice. On the other hand, such differences were not found in nu/nu mice, suggesting that thymus-independent development of T cells is not different among regions. Different local expansion of thymus-dependent alphabeta T cells may cause the regional variations seen in the distribution of alphabeta T cell IELs in +/+ and nu/+ mice.     

Mycoplasma pulmonis arthritis in congenitally athymic (nude) mice. Clinical and biological features

Congenitally athymic BALB/cA nu/nu mice were employed to elucidate the role of the thymus in experimental Mycoplasma pulmonis strain m53 infection, and nu/+ mice were used for comparison. Chronic polyarthritis was frequently produced in both of nu/nu and nu/+ mice by intravenous injection of the organisms. Macroscopically, nu/nu mice developed severer arthritis and a much lower grade of resolution than nu/+ mice. Periarticular abscess, conjunctivitis, and emaciation were observed in some of the nu/nu mice, but not in the nu/+ mice. Mycoplasmas were isolated from joints and other tissues (including periarticular abscesses and eyelids) of infected nu/nu mice at higher frequencies as well as in greater quantities, and did not show any elimination trends for at least 20 weeks after inoculation. However, nu/+ mice, mycoplasmas were almost exclusively located in joints, and distribution of organisms to the other organs disappeared soon after the infection. Increases in complement-fixing antibody titers were not related to the inhibition of mycoplasmal spread. Thymus-dependent functions that may in some way prevent growth and spread of mycoplasmas in mice are discussed.     

POTASSIUM AND AMINO ACID TRANSPORT IN HUMAN LEUKOCYTES EXPOSED TO PHAGOCYTIC STIMULI

Influxes of potassium and amino acids were measured in suspensions of human polymorphonuclear leukocytes (PMNs) under resting conditions and after various phagocytic stimuli. Both ouabain-sensitive (or pump) and ouabain-insensitive (or leak) influxes of K were determined. In 5 mM external K, mean total K influx was 0.69 nmol/10⁶ cells x min, of which 52% was ouabain-sensitive. Ouabain binding was irreversible, and, as in erythrocytes, was inhibited by K. At external concentrations of 0.1 mM, influxes of lysine and leucine were entirely carrier-mediated, with means of 0.021 nmol/10⁶ cells x min, and 0.019 nmol/10⁶ cells x min, respectively. After incubation of PMNs with zymosan or latex particles, the K pump was reduced more than 60%, whereas amino acid influxes were inhibited only by 30%. PMNs were also exposed to cytochalasin B before challenge by particles: the drug prevented phagocytosis but not surface binding of zymosan, nor did it influence transport of K or amino acids. After pretreatment of PMNs with cytochalasin B, interaction of zymosan with their surface resulted in the same degree of inhibition of influxes of K and amino acids as when the cells were permitted to phagocytose the particles. In contrast, exposure of PMN to latex particles, which do not bind to cytochalasin B-treated cells, after pretreatment of cells with cytochalasin B did not result in inhibition of influxes. Treatment of cells with colchicine had no effect on either membrane transport or its inhibition after exposure to various phagocytic stimuli. These results indicate that the surface membranes of PMNs are functionally heterogeneous with respect to the association of transport sites for the different solutes. Moreover, loss of specific membrane functions from phagocytosing cells may result from the surface-at-tachment phase of particle-cell interactions, since the interactions of zymosan particles with PMNs in the absence of phagocytosis also inhibited transport of solutes.