Transfer of Protection to Murine Typhoid Conferred by L-Form Salmonella typhimurium in Dependence of Cooperation between L Form-Adopted Macrophages and L Form-Induced Lyt-2+ T Cells

The effector cells responsible for protection to Salmonella typhimurium in C3H/HeJ mice, conferred by L-form S. typhimurium, were determined by cell transfer test. Nonfractionated spleen cells from 6-week immune mice but not from 24-week immune animals transferred anti-S. typhimurium immunity. Treatment with anti-macrophage antiserum and complement most effectively abolished protective capacity in 6-week immune cells, while anti-T cell monoclonal antibody plus complement reduced it to a lesser extent. However, adoptive protection was achieved only by transfer of immune macrophages along with Lyt-2⁺ T cells selected from 6-week immune spleen cells. These Lyt-2⁺ T cells were cytotoxic to Kupffer cells from C3H/HeJ mice which had been infected 48 hr previously and from the mice which had been immunized 1 week previously, but not to the cells from 6-week immune mice and from normal animals. Moreover, protective capacity in immune macrophages seemed to be correlated to the degree of colonization by the L forms, and the inability to transfer immunity of 24-week immune spleen cells may be due to the decrease in the L form-colonization. These results suggest that cooperation between the L form-colonized macrophages and L form-induced cytotoxic Lyt-2⁺ T cells contributes to anti-S. typhimurium immunity, and might imply the immunological difference between the 6-week immune phagocytes and the cells at an early stage of infection or immunization.     

Trichinella spiralis: the influence of short chain fatty acids on the proliferation of lymphocytes, the goblet cell count and apoptosis in the mouse intestine

This study was carried out to determine the influence of short chain fatty acids (SCFA) on spleen and mesenteric lymph node lymphocyte proliferation, goblet cells and apoptosis in the mouse small intestine during invasion by Trichinella spiralis. BALB/c mice were infected with 250 larvae of T. spiralis. An SCFA water solution containing acetic, propionic and butyric acids (30:15:20 mM) was administered orally starting 5 days before infection and ending 20 days post infection (dpi). Fragments of the jejunum were collected by dissection 7 and 10 dpi, and were examined for apoptotic cells in the lamina propria of the intestinal mucosa, and for goblet cells. The proliferation index of the cultured spleen and mesenteric lymph node lymphocytes with MTT test was also determined. The orally administered SCFA solution decreased the proliferation of mesenteric lymph node lymphocytes in the mice infected with T. spiralis at both examination times, but did not influence the proliferative activity of the spleen cells. Seven dpi, both in the spleen and mesenteric lymph nodes, the highest proliferation index of concanavalin A (Con A)-stimulated lymphocytes was found in the group of uninfected animals receiving SCFA animals. This tendency could still be seen 10 dpi in the mesenteric lymph nodes but not in the spleen, where the proliferation index in this group had significantly decreased. In vitro studies revealed, that butyric and propionic acids added to the cell cultures suppressed the proliferation of Con A-stimulated mesenteric lymph nodes and spleen lymphocytes taken from uninfected and T. spiralis-infected mice. Acetic acid stimulated proliferation of splenocytes taken from uninfected mice but did not affect lymphocyte proliferation in mesenteric lymph nodes from uninfected or infected mice. Orally administered SCFA increased the number of goblet cells found in the epithelium of the jejunum 7 dpi, but this number had decreased 10 dpi. The number of apoptotic cells in the lamina propria of the intestinal mucosa of animals infected with the T. spiralis and receiving SCFA was also lower, particularly 10 dpi. The above results show that SCFA can participate in the immune response during the course of trichinellosis in mice.     

The passive transfer of protective immunity against Angiostrongylus cantonensis with immune lymph node cells from different lymphoid tissues in rats

-Yong W. K. and Dobson C. 1982. The passive transfer of proctective immunity against Angiostrongylus cantonensis with immune lymph node cells from different lymphoid tissues in rats. International Journal for Parasitology12: 423–425. Lymph node cells from the posterior cervical and mesenteric lymph nodes of immune rats passively protected syngeneic recipient rats against Angiostrongylus cantonensis better than cells from the spleen, thymic and inguinal lymph nodes either as reduced worms burdens and/or stunted growth. No antibody was detected in the sera of recipient rats after transfer of the cells and before infection which suggested that the protection was cell- rather than antibody-mediated.     

Immunohistochemical localization of xenogeneic antibodies against Iak lymphocytes on B cells and reticular cells

Rabbit antiserum against B10.AQR mouse spleen and lymph node cells (RAQR), after appropriate absorption, reacted with Ia^k-positive spleen and lymph node cells in cytotoxic and complement-fixing indicator systems. It reacted neither with Ia^k-positive thymocytes nor Ia^k-negative thymocytes, spleen, and lymph node cells. Cryostat sections of tissue from Ia^k-positive and Ia^k-negative mice were incubated with RAQR and either rabbit anti-mouse Ig or rabbit anti-T cell globulin. With the unlabeled antibody enzyme method, RAQR-stained lymphocytes were concentrated in the B-cell regions of spleen and lymph nodes of Ia^k-positive CBA mice. The tissues of mice bearingI-region haplotypes different fromk were negative. Reticular cells of the T cell-supporting network were also positive in Ia^k mice, but liver, gall bladder, and testicular cells were not. Macrophages of both Ia^k-positive and -negative mice were stained by RAQR and also by heat-aggregated, peroxidase-labeled Ig. Ia^k-positive reticular cells survived 900 R total body irradiation and persisted after grafting with Ia^k-negative bone marrow. The reticular cells were also seen in a thymus which was depleted of cortisone-sensitive lymphocytes.Abbreviations used in this paper are as follows RAQR rabbit anti-mouse-B10.AQR globulin - RAMTG rabbit anti-mouse T-cell globulin - RAMIG rabbit anti-mouse Ig - SARIG sheep anti-rabbit Ig - agg-HIg aggregated human Ig - PAP anti-peroxidase-peroxidase-complex     

Impact of aging on immune modulation by tumor

 Tumor development and aging can each alter immune competence. The present study aimed to determine the impact of Lewis lung carcinoma (LLC) presence on immune parameters of middle-aged (averaging 6.5 months) versus aged (averaging 21.3 months) mice. An age-associated decline in the CD4⁺ cell frequency was seen in freshly isolated spleen and lymph node cells, as well as in cultures stimulated with immobilized anti-CD3. This decline was not further exacerbated by tumor presence. What was prominently inhibited by tumor was the capacity of either splenic or lymph node CD4⁺ cells to become stimulated to express IFN-γ. Spleen and lymph node cultures from aged tumor-bearing mice had the lowest frequency of CD4⁺IFN-γ ⁺ cells and the least amount of secreted IFN-γ. CD8⁺ cells were not affected by aging, but tumor presence reduced the induction of CD8⁺IFN-γ ⁺ cells in lymph node cultures. We previously showed that LLC growth stimulates myelopoiesis, as seen by splenomegaly and the mobilization of immune inhibitory CD34⁺ progenitor cells. Tumor presence in middle-aged mice reduced spleen cell blastogenesis, which was mediated by CD34⁺ cells. Aged mice had reduced blastogenesis, and this was further reduced by presence of tumor. However, neither the age-associated immune dysfunction nor the tumor-induced immune suppression in aged mice was due to CD34⁺ progenitor cells. These studies show how tumor presence can further compromise the immune dysfunction that accompanies aging. In addition, they show that aging impacts on the mechanisms by which tumors inhibit T-cell capabilities, with myelopoiesis-associated CD34⁺ cells mediating the immune depression of middle-aged tumor-bearers and an independent mechanism being responsible for the immune depression in aged tumor-bearing mice. Received: 19 March 2001 / Accepted: 4 May 2001     

Some Qualitative Aspects of Spleen Cell Transfer Studies on Plasmodium berghei-Infected Rats*

SYNOPSIS. Adoptive immunity to Plasmodium berghei was transferred by intraperitoneal injections into rats, never before exposed to this parasite, of either 2 × 10⁷ or 2 × 10⁸, but not of 2 × 10⁶, spleen cells from syngenic rats which had recovered from a primary P. berghei infection. When the spleen cells from the latter animals were kept at 47 C for 45 min they remained alive, but no longer were able to transfer protection. The capacity to transfer adoptive immunity was not found in spleen cells from adult rats capable of age immunity. On the other hand, this capacity was found in spleen cells from rats that had suffered a very transient parasitemia (> 1% peak parasitemia).     

A vaccine based on exosomes secreted by a dendritic cell line confers protection against T. gondii infection in syngeneic and allogeneic mice

Our results show that exosomes secreted by SRDC pulsed in vitro with Toxoplasma gondii-derived antigens (Exo-TAg) induced protective responses against infection with the parasite in both syngeneic and allogeneic mice. After oral infection, syngeneic CBA/J mice exhibited significantly fewer cysts in their brains and allogeneic C57BL/6 mice survived. This protection was associated with strong humoral responses in vivo in serum from both CBA/J and C57BL/6 mice, and with high levels of anti-TAg IgA antibodies in intestinal secretions from CBA/J mice alone. Furthermore, strong cellular responses in vivo were observed in both mouse models. Cellular proliferation was associated with cytokines production by spleen and mesenteric lymph node cells. The results presented here show that exosomes are nucleic acid free vesicles that are able to induce immune responses correlated with protection against parasitic infections in both syngeneic and allogeneic mice. They could constitute an efficient tool for use in vaccination and antitumor strategies based on exosomes.     

In vitro development of a primary antibody response with lymph node cells.

Utilizing a variety of lymphoid tissues from three common laboratory species, comparative studies were performed to investigate the competence of the dissociated cells to respond to a heterologous erythrocyte with the development of specific plaque-forming cells. Dissociated spleen cells harvested from BDF1 mice consistently developed specific plaque-forming cells (PFC) to sheep red blood cells (SRBC), while hamster spleen cells inconsistently developed specific antibody-forming cells to SRBC. Under identical conditions, guinea pig spleen cells did not develop significant numbers of PFC to SRBC. However, lymph node cell cultures of all three species tested yielded specific PFC. In the mouse and hamster lymph node cell cultures, the yield of PFC per culture or per 10⁶ recovered viable cells was always greater than the yield from companion spleen cell cultures. Guinea pig mesenteric lymph node cell cultures developed the major PFC response to SRBC, while both mesenteric and peripheral lymph node cell cultures from hamsters were equivalent in their response to SRBC. The data demonstrate that it is possible to develop a primary antibody response to SRBC in vitro utilizing normal endogenous hamster or guinea pig lymphoid cells, if lymph nodes are the source of cells.     

Impairment of lymphocyte mobilization from lymphoid organs by granulomatous infection.

The kinetics of the lymphocytosis induced by intravenous (iv) injection of the lymphocyte mobilizing agent polymethacrylic acid (PMAA) were studied in C3H mice chronically infected with Mycobacterium lepraemurium and in normal controls. After the tenth week of infection, lymphocyte mobilization to peripheral blood by PMAA diminished progressively and at 18 weeks it was significantly less than normal (P < 0.05). ⁵¹Chromium-labeled lymph node cells from syngeneic donors were given iv to 18-week infected or control mice and allowed to home for 18 hr prior to PMAA injection. Radioactivity in the blood of infected mice was significantly less than levels in controls at 2, 4, and 6 hr after PMAA (P = 0.02). Similar studies of splenectomized mice from the normal and infected groups indicated that impairment of lymphocyte mobilization in infected mice was secondary to lymphocyte trapping by the spleen and lymph nodes.     

Two tumor models of curative adoptive chemoimmunotherapy using tumor-infiltrated spleen cells with potent antitumor cytotoxicity stimulated by antigen-sharing tumors

Previously we have established curative protocols for adoptive chemoimmunotherapy (ACIT) of mice bearing different plasmacytomas that are known to bear cross-reacting antigens: (a) the cure of mice bearing an early-stage, nonpalpable MOPC-315 tumor by a very low dose of cyclophosphamide (10 mg/kg) and cultured MOPC-315-tumor-infiltrated (TI) spleen cells (25×10⁶) and (b) the cure of mice bearing a late-stage, relatively drug-resistant, highly metastatic RPC-5 tumor with cyclophosphamide (100 mg/kg) and cultured RPC-5 TI spleen cells (25×10⁶–50×10⁶). In both models, the spleen cells were obtained from mice bearing a late-stage tumor and were cultured for 5 days in the presence of polyethyleneglycol 6000 and autochthonous tumor cells as a source of tumor antigen. Here we show that RPC-5 tumor cells could substitute for MOPC-315 tumor cells in the 5-day culture of MOPC-315 TI spleen cells so that they became curative in ACIT for mice bearing an early-stage MOPC-315 tumor. Similarly, MOPC-315 tumor cells could substitute for RPC-5 tumor cells in the 5-day culture of RPC-5 TI spleen cells so that they became curative in ACIT of mice bearing a late-stage RPC-5 tumor. In addition, RPC-5 TI spleen cells cultured with either MOPC-315 or RPC-5 tumor cells were effective in curing all mice bearing an early-stage MOPC-315 tumor by ACIT. However, MOPC-315 TI spleen cells whether cultured with MOPC-315 or RPC-5 tumor cells, were much less effective than cultured RPC-5 TI spleen cells in curing mice bearing a late-stage RPC-5 tumor by ACIT (although the survival of these mice was extended significantly). Interestingly, whereas RPC-5 TI spleen cells cultured with either MOPC-315 or RPC-5 tumor cells were as effective as MOPC-315 TI spleen cells cultured under the same conditions in lysing MOPC-315 tumor cells in vitro, MOPC-315 TI spleen cells that had been cultured with either MOPC-315 or RPC-5 tumor cells exerted a much weaker in vitro cytotoxic T lymphocyte activity against RPC-5 tumor cells than did RPC-5 TI spleen cells that had been cultured under the same conditions.Work was supported by research grant CA-30088 from the National Cancer Institute and IM-435 from the American Cancer Society. M. B. M. was supported by Career Development Award CA-01350 from the National Cancer InstituteThis work is in partial fulfillment of the requirements for the Ph. D. degree     

Adjuvant Activity of Mycobacterial Fractions

A quantitative assay and characterization of oil-attached cell wall of Mycobacterium bovis BCG (BCG-CWS) which stimulates cell-mediated immunity of spleen cells to alloantigens in mice were carried out by an in vitro cell-mediated cytotoxicity test using ⁵¹Cr-labeled target cells. C57BL/6J mice (H-2^b) were immunized intraperitoneally with mastocytoma cells (H-2^d) with or without oil-attached BCG-CWS. The cytotoxicity, comparable to that of spleen cells from mice immunized with mastocytoma cells (3 × 10⁷), could be induced in spleens of mice immunized with a mixture of mastocytoma cells (10⁴) and oil-attached BCG-CWS. The enhancing effect persisted for 55 days or more after the alloantigenic immunization. Oil-attached BCG-CWS enhanced cell-mediated cytotoxicity of T cells in the spleen and the mesenteric lymph node, but not in the thymus. The cytotoxicity showed specificity toward the alloantigen used for immunization. In addition to BCG-CWS, the cell walls of Nocardia rubra and Corynebacterium diphtheriae PW8 and the peptidoglycolipids of Mycobacterium tuberculosis Aoyama B were found to be potent stimulants of cell-mediated cytotoxicity in mice. Oil-attached BCG-CWS did not enhance humoral response to mastocytoma cells but enhanced cell-mediated cytotoxicity when viable mastocytoma cells were used as antigen. The above result was supported by the fact that anti-hapten antibody response induced by viable trinitrophenyl (TNP)-mastocytoma cells (10⁴) plus oil-attached BCG-CWS did not increase to the maximum level as was observed in mice immunized with a larger number of mastocytoma cells (3 × 10⁷) alone, while cell-mediated cytotoxicity induced by the same treatment increased to the maximum level obtained by immunization with mastocytoma cells (3 × 10⁷) alone.     

The influence of cyclophosphamide on antitumor immunity in mice bearing late-stage tumors

Spleen cells from mice bearing late-stage methylcholanthrene-induced tumor did not show any tumor activity when mixed with tumor cells in Winn's assay. Treatment of these mice with cyclophosphamide (CY) induced a tumor-inhibitory activity in spleen, occurring on day 7 after treatment, reaching its maximum on day 11 and disappearing by day 21. This antitumor activity could not be induced in control, tumor-free or T-deficient tumor-bearing mice. CY-induced tumor-inhibitory activity was immunologically specific, and mediated by Thy-1⁺, L3T4^–, Ly-2⁺ cells. Contrary to spleen cells from untreated tumor-bearing mice, spleen cells from CY-treated tumor-bearing mice did not suppress the antitumor activity of immune spleen cells in Winn's assay. However, in contrast to immune spleen cells, CY-induced tumor-inhibitory cells did not manifest antitumor activity when transferred systemically (i. v.) into T-cell-deficient tumor-bearing mice. Even more, spleen cells from CY-pretreated mice, harvested 7–15 days after the drug administration, partially suppressed the antitumor activity of concomitantly transferred spleen cells from specifically immune mice. Nevertheless, CY-pretreated mice manifested concomitant immunity, i.e. these mice exhibited higher resistance to a second inoculum of the same tumor than did nontreated mice or even mice with excised primary tumor.     

Activation and route of administration both determine the ability of bone marrow-derived dendritic cells to accumulate in secondary lymphoid organs and prime CD8<Superscript>+</Superscript> T cells against tumors

Aims

To examine the effects of route of administration and activation status on the ability of dendritic cells (DC) to accumulate in secondary lymphoid organs, and induce expansion of CD8⁺ T cells and anti-tumor activity.

Methods

DC from bone marrow (BM) cultures were labeled with fluorochromes and injected s.c. or i.v. into naïve mice to monitor their survival and accumulation in vivo. Percentages of specific CD8⁺ T cells in blood and delayed tumor growth were used as readouts of the immune response induced by DC immunization.

Results

The route of DC administration was critical in determining the site of DC accumulation and time of DC persistence in vivo. DC injected s.c. accumulated in the draining lymph node, and DC injected i.v. in the spleen. DC appeared in the lymph node by 24 h after s.c. injection, their numbers peaked at 48 h and declined at 96 h. DC that had spontaneously matured in vitro were better able to migrate compared to immature DC. DC were found in the spleen at 3 h and 24 h after i.v. injection, but their numbers were low and declined by 48 h. Depending on the tumor cell line used, DC injected s.c. were as effective or more effective than DC injected i.v. at inducing anti-tumor responses. Pre-treatment with LPS increased DC accumulation in lymph nodes, but had no detectable effect on accumulation in the spleen. Pre-treatment with LPS also improved the ability of DC to induce CD8⁺ T cell expansion and anti-tumor responses, regardless of the route of DC administration.

Conclusions

Injection route and activation by LPS independently determine the ability of DC to activate tumor-specific CD8⁺ T cells in vivo.

     

Tolerance induction to a thymus-dependent antigen in vitro: treatment of nonadherent cells with tolerogen biologically filtered in vitro

Highly tolerogenic bovine gamma globulin (BGG), a thymus-dependent antigen, was prepared by biologic filtraration in vitro. It readily induced tolerance in vivo in BALB/c mice and also rendered their nonadherent lymph node cells tolerant after in vitro incubation. Biologic filtration in vitro was carried out by incubating 2.5 × 10⁷ lymph node cells with 10 mg of nontolerogenic BGG in 10 ml of Eagle's medium containing 2% normal mouse serum at 37 °C for 6 hr. The BGG-containing medium was clarified by centrifugation and was used without further dilution.For tolerance induction in vitro, lymph node cells were separated into adherent and nonadherent populations on Falcon plastic. These cells were incubated for 0–18 hr at 37 °C with biologically filtered BGG (bBGG). After incubation, the cells were washed three times and (2–2.5) × 10⁷ nonadherent or 4 × 10⁶ adherent cells were injected iv with their untreated counterpart into lethally irradiated mice which had received 10⁶ bone marrow cells. The recipients were then challenged with 300 μg of aggregated BGG, and tolerance was assayed by the elimination of labeled BGG, rosette formation, and passive hemagglutination. Spleen cells were similarly treated for comparison. Our findings show that tolerance was not induced in vitro in adherent lymph node cells. However, in the nonadherent populations, those from the lymph node but not the spleen were rendered tolerant. The acquisition of tolerance in vitro was gradual. It was dependent upon the length of exposure to bBGG and required at least 6 hr.     

T-cell mediated suppression in the MRL mouse

MRL/lpr mice possess an autosomal recessive gene, lpr, which is associated with lymphoproliferation and acceleration of autoimmune disease. Lymphoproliferation has been ascribed to a single gene defect predominantly affecting the T-lymphocyte component of the immune system. MRL/++ mice do not possess the lpr autosomal recessive mutation and do not develop early lymphadenopathy. T-lymphocyte functional activity was studied in these mice using the polyclonal T-cell mitogens PHA and Con A. Our results indicated a significant suppression of the spleen and lymph node response of MRL/lpr mice to these polyclonal mitogens as compared to the MRL/++ response noted as early as 6 weeks of age. In addition, there was a progressive decline in the MRL/lpr spleen and lymph node cell mitogenic responses with increasing age. Spleen and lymph node cells from 20-week MRL/lpr mice were also relatively unresponsive in the mixed lymphocyte culture reaction as compared to cells from MRL/ ++ or BALB/c mice. The in vitro proliferative response of the MRL mice was further examined with respect to possible accessory cell modulation by both macrophages and T cells. It was found that in 20-week MRL/lpr lymph nodes a significant degree of suppression of lymphocyte proliferation could be mediated by the MRL/lpr T cell. Increased lymphocyte proliferation to a mitogenic signal could only be demonstrated in those MRL/lpr mice 3 weeks of age.     

Prostaglandin synthesis by lymphoid tissue of mice experiencing a graft-versus-host reaction: relationship to immunosuppression

Studies were carried out on the induction of PGE synthesis during the GVH reaction and its role in GVH-induced immunosuppression. The results demonstrated that spleen, lymph node cells and, to a much lesser degree, thymus cells obtained from adult C57BL/6 × AF₁ mice treated with 50–75 × 10⁶ C57BL/6 lymphoid cells were stimulated to produce PGE during the course of the GVH reaction. The spleen and lymph node PGE production peaked at Day 9 post-GVH induction (30- and 15-fold higher than normal, respectively). Thereafter, it declined to near normal levels by Days 25–30 post-GVH induction. Passage of GVH spleen cells through a rayon column removed macrophages but not mitogen-responsive T and B cells and also removed nearly all of the PGE-producing cells, except during the later course of the GVH reaction. Removal of PGE-producing cells from GVH-immunosuppressed spleen cells significantly reconstituted the mitogen response to PHA and LPS. Treatment of mice experiencing a GVH reaction with indomethacin delayed the onset of suppression of the plaque-forming cell response to sheep erythrocytes. These results suggest that early GVH-induced immunosuppression which may represent an amplified normal regulatory mechanism is mediated by increased macrophage production of PGE which suppresses both B- and T-cell functions, whereas at later stages other immunosuppressive mechanisms become operational.     

Single-Cell Analysis Reveals Isotype-Specific Autoreactive B Cell Repertoires in Sj?gren’s Syndrome

Microengraving is a novel technology that uses an array of microfabricated subnanoliter wells to isolate and characterize secreted proteins from larger number of single cells. This printing technique permits the capture and characterization of secreted antibodies on glass slides. Here, we profiled the antigenic repertoires of B cells reacting against salivary gland tissues in Sjögren’s syndrome (SjS), an autoimmune disease targeting the exocrine glands. Single-cell suspensions of spleen and cervical lymph node cells prepared from normal C57BL/6 and SjS-susceptible (SjS^s) C57BL/6.NOD-AecAec2 mice were dispersed into subnanoliter wells (nanowells). Capture slides preincubated with mouse immunoglobulins were used for printing. Detection antibodies included fluorescence conjugated anti-IgG1, salivary gland lysates of C57BL/6 and SjS^s mice. Results indicate an increase in the frequency of IgG1-secreting cells in the spleen of SjS^s mice compared to C57BL/6 mice. Cells from the lymph node of SjS^s mice yield higher instances of IgG1 reactive against salivary gland antigens than cells from the lymph nodes of C57BL/6 mice. These data demonstrate the isotype-specific reactivity of antibodies during the autoimmune process, and further reveals significant differences in the non-autoimmune and autoimmune antibody repertoires. These results support the generation of self-reactive B cell repertoires during the autoimmune process, at the same time, verifying that microengraving of single cells might allow for identification of novel biomarkers in SjS.     

Transfer of immunity to Babesia microti of human origin using T lymphocytes in mice

Lymph node and spleen cells from mice infected with Babesia microti of human origin developed the ability to transfer adoptive immunity to naive mice within 25 days after infection. This protective activity was greater in cells obtained at 32 days than in cells obtained at 25 days postinfection and remained stable up to 52 days postinfection. Recipients of lymph node cells and spleen cells displayed similar peak parasitemias although 2 days after peak parasitemia, immune spleen cell recipients had significantly lower parasitemias than immune lymph node cell recipients. Strong protective activity was demonstrated when cells were transferred 1 day postinfection, while equal numbers of cells, transferred 3 days postinfection did not confer significant protection over nonimmune cells. There was also a suggestion that the number of immune spleen cells necessary for significant protection was directly related to the number of parasites inoculated. The subpopulation of lymphocytes responsible for the transfer of adoptive immunity to B. microti of human origin was then studied in BALB/c mice depleted of T lymphocytes by thymectomy and lethal irradiation. One day after infection with B. microti, T-cell-depleted mice were given complement-treated immune spleen cells, anti-θ serum-treated immune spleen cells, nonimmune spleen cells, or no cells. Similar experiments were performed comparing the effects of anti-immunoglobulin serum-treated and unfractionated immune spleen cells on B. microti parasitemia. Treatment with anti-θ serum abrogated the protective activity of immune spleen cells while anti-immunoglobulin serum treatment had no effect. These results suggest that immunologic memory of B. microti in BALB/c mice is modulated by T rather than B lymphocytes.     

Studies of murine lymphocytes and alloantigens: I. Ly-6 mitogen and MLR responses

Antisera to the mouse lymphocyte surface alloantigens Ly-6.1 and Ly-6.2 were used to further study the functional distribution of these antigens. After selective depletion with antiserum + rabbit complement (RC), lymph node or spleen cells from Ly-6 congenic (C3H and C3H.B6-Ly-6^b) and noncongenic strains of mice were tested for: (a) their proliferative responses to T- and B-cell mitogens; and (b) their proliferative responses to alloantigens, or ability to stimulate in the MLR. Lymphoid cells required in the proliferative responses to the mitogens leucoagglutinin, concanavalin A (Con A), lipopolysaccharide (LPS), and pokeweed mitogen (PWM) were Ly-6⁺. Lymph node responder cells in the mixed lymphocyte reaction (MLR) were also Ly-6⁺, whereas spleen stimulator cells were Ly-6^?. Treatment of lymph node cells with anti-Ly-6 sera in the absence of RC had no specific blocking effect on the response to any of these mitogens. The studies indicate that the Ly-6 antigen is a potentially valuable marker for distinguishing between functionally distinct Ly-1⁺ T-cell subsets.     

Plasmodium berghei: Heat-treated sporozoite vaccination of mice

Repeated intravenous (IV) immunizing injections with 25,000 Plasmodium berghei heat-treated sporozoites gave an average protection of 13% in five experiments (0–53%). Four injections of 10⁵ sporozoites gave 50% protection, seven injections of 10⁵ gave 37% protection, and six injections of 10⁵ gave 11% protection. Viable spleen cells (1.2 × 10⁸) from twice challenged immune syngenic mice did not protect naïve mice against iv challenge. Six ip injections of the supernatant of Parr Bomb disintegrated sporozoites gave no protection against ip challenge, but 7 ip injections gave 40% protection. Centrifuged pellets from French Pressure Cell-disintegrated sporozoites gave almost no protection either iv, sc, or ip. The supernatant was disc-electrophoresed and compared to normal mosquito heads and salivary glands in order to select sporozoite bands for immunizing injections. Results were discussed with respect to uniformity of antigen batches.