A combined method for both endogenous myeloperoxidase and acid phosphatase cytochemistry as well as immunoperoxidase surface labelling discriminating human peripheral blood-derived dendritic cells and monocytes

Summary On light microscopical (LM) level dendritic cells (DC) isolated from lymphoid organs can be discriminated from macrophages (Mø) by the presence of acid phosphatase (APh) activity in a spot near the nucleus and constitutional expression of class II antigens. The aim of our study was to investigate whether DC and monocytes (Mo) enriched from human peripheral blood could be discriminated on the electron microscopical (EM) level. Therefore we developed a triple method by which we compared the presence of myeloperoxidase (MPO) containing vesicles, the localization of APh containing vesicles and expression of MHC class II and RFD1 (a DC-associated class II-like antigen) plasmamembrane antigens. DC, functionally characterized as potent stimulators in a MLR, are MPO-negative, whereas Mo show MPO in cytoplasmic granules. Although both DC and Mo show little APh activity at LM level, both types of cells show APh activity at the EM level but at different locations. In DC APh containing vesicles are present in a distinct juxtanuclear area, in contrast to Mo, which show APh activity in lysosomes scattered throughout the whole cytoplasm. Moreover, on both LM and EM level, DC are strongly class II positive, whereas Mo show variable labelling intensity for class II, while RFD1 was only found on DC.     

A combined method for both endogenous myeloperoxidase and acid phosphatase cytochemistry as well as immunoperoxidase surface labelling discriminating human peripheral blood-derived dendritic cells and monocytes.

On light microscopical (LM) level dendritic cells (DC) isolated from lymphoid organs can be discriminated from macrophages (M phi) by the presence of acid phosphatase (APh) activity in a spot near the nucleus and constitutional expression of class II antigens. The aim of our study was to investigate whether DC and monocytes (Mo) enriched from human peripheral blood could be discriminated on the electron microscopical (EM) level. Therefore we developed a triple method by which we compared the presence of myeloperoxidase (MPO) containing vesicles, the localization of APh containing vesicles and expression of MHC class II and RFD1 (a DC-associated class II-like antigen) plasma-membrane antigens. DC, functionally characterized as potent stimulators in a MLR, are MPO-negative, whereas Mo show MPO in cytoplasmic granules. Although both DC and Mo show little APh activity at LM level, both types of cells show APh activity at the EM level but at different locations. In DC APh containing vesicles are present in a distinct juxtanuclear area, in contrast to Mo, which show APh activity in lysosomes scattered throughout the whole cytoplasm. Moreover, on both LM and EM level, DC are strongly class II positive, whereas Mo show variable labelling intensity for class II, while RFD1 was only found on DC.     

Delayed-type hypersensitivity to minor histocompatibility antigens and its genetic restriction

The analysis of skin allograft survival time and the level of delayed-type hypersensitivity (DTH) reaction to major and minor histocompatibility antigens revealed the correlation between these parameters of the transplantation immunity. The data obtained have shown that histocompatibility in several non-H-2 antigens induces DTH reaction comparable with the reaction caused by H-2 antigens. The effector phase of DTH to non-H-2 antigens is H-2 restricted. No restriction of the afferent phase is revealed. The application of these results to the analysis of the mechanisms of the recognition of minor histocompatibility antigens in DTH is discussed.     

Trans-vivo Delayed Type Hypersensitivity Assay for Antigen Specific Regulation

Delayed-type hypersensitivity response (DTH) is a rapid in vivo manifestation of T cell-dependent immune response to a foreign antigen (Ag) that the host immune system has experienced in the recent past. DTH reactions are often divided into a sensitization phase, referring to the initial antigen experience, and a challenge phase, which usually follows several days after sensitization. The lack of a delayed-type hypersensitivity response to a recall Ag demonstrated by skin testing is often regarded as an evidence of anergy. The traditional DTH assay has been effectively used in diagnosing many microbial infections.Despite sharing similar immune features such as lymphocyte infiltration, edema, and tissue necrosis, the direct DTH is not a feasible diagnostic technique in transplant patients because of the possibility of direct injection resulting in sensitization to donor antigens and graft loss. To avoid this problem, the human-to-mouse "trans-vivo" DTH assay was developed ^1,2. This test is essentially a transfer DTH assay, in which human peripheral blood mononuclear cells (PBMCs) and specific antigens were injected subcutaneously into the pinnae or footpad of a naïve mouse and DTH-like swelling is measured after 18-24 hr ³. The antigen presentation by human antigen presenting cells such as macrophages or DCs to T cells in highly vascular mouse tissue triggers the inflammatory cascade and attracts mouse immune cells resulting in swelling responses. The response is antigen-specific and requires prior antigen sensitization. A positive donor-reactive DTH response in the Tv-DTH assay reflects that the transplant patient has developed a pro-inflammatory immune disposition toward graft alloantigens.The most important feature of this assay is that it can also be used to detect regulatory T cells, which cause bystander suppression. Bystander suppression of a DTH recall response in the presence of donor antigen is characteristic of transplant recipients with accepted allografts ^2,4-14. The monitoring of transplant recipients for alloreactivity and regulation by Tv-DTH may identify a subset of patients who could benefit from reduction of immunosuppression without elevated risk of rejection or deteriorating renal function.A promising area is the application of the Tv-DTH assay in monitoring of autoimmunity^15,16 and also in tumor immunology ¹⁷.     

Characterization of the population of phagocytic cells in thymic cell suspensions

Rat thymic phagocytic cells were characterized in vitro using various light- and electron-microscopical techniques. Thymic cell suspensions were mechanically prepared and enriched for non-lymphoid cells, which were predominantly phagocytic and of three types. Type I showed acid phosphatase (APh) activity in small granules dispersed throughout the cytoplasm and were mostly Ia antigen-positive, although the Ia membrane label varied in intensity and distribution among individual cells. Only a few cells had endogenous peroxidase activity. The type-I cells could not be clearly distinguished morphologically from type-II or -III cells, and most likely comprise precursors of both these cell types. Type-II were large pale cells with many slender cell processes. These cells had APh activity centrally positioned, were strongly positive for Ia on the cell membrane and were negative for endogenous peroxidase. The cytoplasm frequently contained Birbeck granules, which unequivocally classifies these cells as the in vitro equivalent of the interdigitating cells present in the medullary area of the thymus in situ. Type-III cells were rounded with a smooth or ruffled cell membrane and contained vacuoles and many phagolysosomes. They were strongly positive for APh which was present throughout the cytoplasm. About 50% of these cells were positive for endogenous peroxidase in a pattern resembling resident macrophages. The cells were negative for Ia antigens. Type-III cells mostly likely represent the macrophages found in the cortical area of the thymus.     

Regulatory mechanisms of cutaneous delayed-type hypersensitivity. II. Suppression of cutaneous delayed-type hypersensitivity by macrophage disappearance reaction

Studies were performed on the behavior of cutaneous delayed-type hypersensitivity (DTH) in guinea pigs in which macrophage disappearance reaction (MDR) was induced. Guinea pigs were immunized with dinitrophenylated egg albumin (DNP-EA), followed by intraperitoneal (ip) injection of liquid paraffin in order to elicit peritoneal macrophages. Subsequently 20 micrograms of EA was injected into these animals and the animals were divided into two groups. One group of animals was sacrificed for estimation of MDR 6 hr after the subsequent ip injection. The other group received a skin test by EA at the time of the subsequent ip injection. The first group of animals sacrificed for estimation of MDR exhibited a marked reduction in the number of peritoneal macrophages. The second group of animals that received skin tests revealed suppressed skin reactions 24 hr after the subsequent ip injection. A similar experiment was performed using the guinea pigs doubly immunized with DNP-EA and dinitrophenylated bovine gamma-globulin (DNP-BGG). Induction of MDR was performed by ip injection of BGG and skin tests were done by both EA and BGG. As a result, suppression of not only BGG-induced skin reactions but also EA-induced skin reactions was observed in animals in which MDR had been induced by BGG. In addition, the guinea pigs in which MDR was induced showed hyporeactivity to phytohemagglutinin (PHA). Reactivity to skin reactive factor (SRF) was also suppressed in these animals. The culture supernatants of macrophages incubated with the MIF fraction in vitro showed the ability to suppress skin reactions of cutaneous DTH, PHA and SRF.     

Induction of cell-mediated immunity to chemically modified antigens in guinea pigs. II. The interaction between lipid-conjugated antigens, macrophages, and T lymphocytes.

Protein antigens covalently conjugated with lipid groups (dodecanoic acid) have previously been shown to stimulate strong delayed-type hypersensitivity (DTH) without the aid of adjuvants. The present experiments show that lipid-conjugated bovine serum albumin (L-BSA) is taken up in vitro by macrophages (Mpsi) 25- to 50-fold more than unconjugated BSA or aminidated BSA, neither of which induces DTH. Macrophages that take up 125I-labeled L-BSA in vitro stimulate DTH even more efficiently, when injected into syngeneic guinea pigs, than does soluble L-BSA. Tracer studies on the fate of radiolabeled BSA and L-BSA showed that much more L-BSA than BSA was retained by draining lymph nodes. Autoradiography demonstrated that 125I-L-BSA is rapidly taken up by Mpsi in the medullary sinuses of the lymph nodes. Some of this antigen is then transported into the paracortex, a region in which T lymphocytes predominate. The capacity of lipophilic antigens to stimulate cell-mediated immune responses may be caused by their increased uptake by Mpsi, resulting in more efficient presentation to immunocompetent T lymphocytes. The anatomical site of this Mpsi-T cell interaction may be within the sinusoids or paracortex of the draining lymph nodes.     

Antigen presentation by Langerhans cells in vivo: donor-derived Ia+ Langerhans cells are required for induction of delayed-type hypersensitivity but not for cytotoxic T lymphocyte responses to alloantigens

T cell activation in response to allogeneic stimulation and hapten-specific delayed-contact hypersensitivity responses in vivo can be initiated by Ia-bearing epidermal Langerhans cells (LC). By using a murine heterotopic corneal allograft model, we have investigated the requirement for allogeneic LC as antigen-presenting cells (APC) in the in vivo induction of delayed-type hypersensitivity (DTH) and cytolytic T lymphocyte (CTL) responses to alloantigens in fully allogeneic and H-2 I region-disparate strain combinations. LC-deficient, avascular central corneal allografts from BALB/c donors failed to induce DTH responsiveness when grafted to a subdermal bed on C57BL/6 recipients (p greater than 0.05), yet antigen-specific primary CTL reactivity developed within 7 days after grafting. LC-containing corneal-limbus allografts or central corneal allografts containing a latex bead-induced infiltrate of LC resulted in intense DTH as well as CTL responsiveness when grafted in this same strain combination. Similarly, LC-containing but not LC-deficient corneal allografts from A.TL donors induced DTH responsiveness in I region-disparate A.TH hosts despite the fact that these grafts survived for prolonged duration (less than 28 days). By contrast, CTL induction in I region-disparate hosts was independent of the presence of allogeneic LC. Corneal epithelial cells of grafts removed from I region-disparate hosts 7 days posttransplantation were shown by immunohistology to express the Iak antigens of donor origin. The possibility that bone marrow-derived allogeneic LC were a sufficient requirement for DTH induction was confirmed in experiments performed with CB6F1----B6 bone marrow chimeras used as corneal allograft donors. Corneal-limbus grafts obtained from mice 90 days after chimerization were shown by immunohistology to contain Iad-bearing CB6F1 LC as a sole source of class II alloantigens. When grafted to C57BL/6 recipients, LC-containing chimeric corneas induced DTH responsiveness that was similar in magnitude to that observed in C57BL/6 mice grafted with chimeric skin, yet no DTH response to LC-deficient chimeric central corneal grafts was observed. Moreover, in all cases, the chimeric corneal and skin allografts survived for prolonged duration (greater than 28 days). These results demonstrate that donor-derived LC act as APC in the induction of DTH responsiveness to allogeneic tissue; however, there was no apparent requirement for allogeneic LC in the induction of CTL responses to class I or class II MHC alloantigens.(ABSTRACT TRUNCATED AT 400 WORDS)     

Delayed-type hypersensitivity to elastase-soluble lung peptides in the tight-skin (Tsk) mouse

The development of immunity to homologous connective tissue antigens was studied with respect to aging in the tight-skin (Tsk) mouse mutant. A delayed-type hypersensitivity (DTH) response to elastase-solubilized lung peptides in Tsk/+ mice, which became evident at 10 weeks of age and increased in intensity until 22 weeks, was observed. Tsk mice did not demonstrate significant DTH responses when challenged with type I or IV collagen, and normal (+/+) littermates of all ages did not respond to any of the antigens under study. DTH responses could be adoptively transferred to normal +/+ and C57BL/6 mice with spleen cells from 30-week-old Tsk/+ mice; treatment with anti-Thy 1.2 antibodies plus complement significantly reduced the ability of these Tsk/+ cells to transfer DTH reactivity. No antibody activity to the antigens under study could be detected in the sera of Tsk/+ or +/+ mice at any age. These results are discussed with regard to the pathological manifestations observed in the Tsk/+ mutant mouse.     

Gene expression in the elicitation phase of guinea pig DTH and CHS reactions

Delayed-type hypersensitivity (DTH) reactions are divided into classical DTH induced by protein antigens and contact hypersensitivity (CHS) induced by haptens. It has been reported that different cytokines and T cell subsets are involved in the induction of each DTH reaction. We previously isolated many genes whose expression is elevated during elicitation of skin DTH reaction in guinea pigs. In this study, we focused on the expression of tryptophanyl-tRNA synthetase (WRS), ferritin heavy chain and major histocompatibility complex (MHC) class II genes to investigate the different regulatory mechanisms in classical DTH and CHS. Furthermore, the expression of various cytokines and chemokines was examined. WRS expression in classical DTH was higher than that in CHS, and the expression of interferon-gamma but not that of transforming growth factor-beta showed similar patterns. MHC class II mRNA increased only in classical DTH. The differential expression of WRS and MHC class II genes in classical DTH might be caused by the differential expression of interferon-gamma and/or the involvement of CD4(+) T cells in classical DTH, respectively. In contrast, the expression of ferritin heavy chain and interleukin-1beta was elevated in CHS, and also by treatment with dinitrochlorobenzene in unsensitized guinea pigs, and expression of both was correlated.     

Experimental allergic encephalomyelitis: basic protein regions responsible for delayed hypersensitivity

Three separate peptide regions were isolated from the chymotrypsin digest of the encephalitogenic basic protein from bovine myelin of the central nervous system. The peptides induced delayed type hypersensitivity (DTH) and elicited delayed skin reactivity in experimental animals. However, none of the isolated peptides was capable of inducing experimental allergic encephalomyelitis (EAE). The amino acid sequence of peptide CTP-3 (Gly-Ala-Glu-Gly-Gln-Lys-Pro-Gly-Phe-OH) and peptide CTP-la were found to overlap the C-terminal sequence of encephalitogenic peptides E (residue 112–125) and T8 (residue 65–74) of the basic protein, respectively. The third DTH inducing peptide, CB1-T1, (N-Acetyl-Ala-Ser-Ala-Gln-Lys-OH) was found to overlap the N-terminal sequence of the basic protein molecule. Common to the three DTH inducing peptides, to the basic protein and to the encephalitogenic peptides E-S and T8S is the X-X-X-Gln-Lys sequence. Isolation of the regions of the basic protein that are responsible for DTH provides antigens for the study of the mechanism of cellular immunity in EAE.     

Characterization of the suppressor cell(s) responsible for anterior chamber-associated immune deviation (ACAID) induced in BALB/c mice by P815 cells

Anterior chamber-associated immune deviation (ACAID) is a complex set of immune responses induced by the inoculation of antigens into the anterior chamber of the eye. Histocompatibility antigens, tumor-specific antigens, reactive haptens, and viral antigens have been shown to induce this phenomenon, which comprises the following specific host responses: high titer humoral antibodies, primed cytotoxic T cells, but specifically, impaired skin graft rejection and delayed-type hypersensitivity (DTH). Using the model system of ACAID induced by inoculation of P815 mastocytoma cells into the anterior chambers of H-2-compatible, but minor H-incompatible, BALB/c mice, we demonstrate that the impaired capacity of these animals to develop and express DTH is due to the activation of suppressor T cells. Generation of these cells requires an intact spleen, is not inhibited by cyclophosphamide pretreatment, and is abrogated by systemic treatment of the host with anti-I-J monoclonal antibodies. This splenic suppressor cell(s) can transfer suppression of DTH adoptively to naive syngeneic mice. One suppressor cell is Thy-1.2, Lyt-2.2, and I-Jd positive. A minority of these cells (or a second population of suppressor cells) also expresses the L3T4 surface marker. Suppression is exerted on the efferent limb of DTH expression, although afferent suppression is not excluded. P815-induced ACAID suppressor cells resemble similar cells induced by haptenated spleen cells inoculated into the anterior chamber of the eye. We propose that induction of these suppressor cells, whose target of action is selective for T DTH cells, but not for other types of T cells, is responsible for the phenomenon of immune privilege in the anterior chamber of the eye.     

Correlation between active rosette formation and delayed cutaneous hypersensitivity in experimental allergic encephalomyelitis

The effect of encephalitogenic myelin basic protein, BP, on active rosette-forming T cells (ARFC) was compared to that of nonencephalitogenic peptide S42, a synthetic analogue of the tryptophan region of BP. Depression of ARFC by these antigens was reversible within 24 h after a second dose of the antigen into the skin, or after in vitro incubation of lymphocytes with the sensitizing antigen (Ag-ARFC). The ratio of Ag-ARFC to ARFC rose with time following the sensitization but fell shortly before the clinical onset of experimental allergic encephalomyelitis in animals sensitized with BP. In contrast, the Ag-ARFC/ARFC ratios for animals sensitized with peptide S42 reached plateau levels from which they did not drop. The kinetics of the Ag-ARFC/ARFC responses paralleled those for delayed-type skin hypersensitivity (DTH) in the respective animals. The DTH responses rose following sensitization and fell shortly after the appearance of clinical signs of EAE. The results of this study provide in vitro and in vivo evidence for sensitization to myelin basic protein, and focus attention on the ARFC as a measure for an immunologically active cell population which may be quantitated by antigenic stimulation.Abbreviations used in this report EAE experimental allergic encephalomyelitis - DTH delayed-type skin hypersensitivity - ARFC active rosette-forming T cells - Ag-ARFC antigen-stimulated active rosette-forming T cells - TRFC total rosette-forming T cells     

Effect of treatment with cyclophosphamide in low doses upon the onset of delayed type hypersensitivity in mice chronically infected with Trypanosoma cruzi: involvement of heart interstitial dendritic cells

Acute infection with Trypanosoma cruzi results in intense myocarditis, which progresses to a chronic, asymptomatic indeterminate form. The evolution toward this chronic cardiac form occurs in approximately 30% of all cases of T. cruzi infection. Suppression of delayed type hypersensitivity (DTH) has been proposed as a potential explanation of the indeterminate form. We investigated the effect of cyclophosphamide (CYCL) treatment on the regulatory mechanism of DTH and the participation of heart interstitial dendritic cells (IDCs) in this process using BALB/c mice chronically infected with T. cruzi. One group was treated with CYCL (20 mg/kg body weight) for one month. A DTH skin test was performed by intradermal injection of T. cruzi antigen (3 mg/mL) in the hind-footpad and measured the skin thickness after 24 h, 48 h and 72 h. The skin test revealed increased thickness in antigen-injected footpads, which was more evident in the mice treated with CYCL than in those mice that did not receive treatment. The thickened regions were characterised by perivascular infiltrates and areas of necrosis. Intense lesions of the myocardium were present in three/16 cases and included large areas of necrosis. Morphometric evaluation of lymphocytes showed a predominance of TCD8 cells. Heart IDCs were immunolabelled with specific antibodies (CD11b and CD11c) and T. cruzi antigens were detected using a specific anti-T. cruzi antibody. Identification of T. cruzi antigens, sequestered in these cells using specific anti-T. cruzi antibodies was done, showing a significant increase in the number of these cells in treated mice. These results indicate that IDCs participate in the regulatory mechanisms of DTH response to T. cruzi infection.     

Compartmentalization of choline and acetylcholine metabolism in cultured sympathetic neurons

Although the cellular and molecular mechanisms underlying the delayed-type hypersensitivity (DTH) reaction have been investigated, the functions of infiltrating leukocytes and skin resident cells in the elicitation phase of the DTH reaction are not completely understood. To gain more insight into the role of these cells in the DTH reaction, we identified about 250 cDNA fragments showing elevated expression during the DNCB-induced guinea pig skin DTH reaction by differential display analysis. Characterization of 50 of them led to the identification of 28 genes whose expression was elevated in the DNCB-induced DTH reactive tissue. Sequencing of the 28 cDNA fragments and homology search analysis demonstrated that 10 of them represented known genes, some of which, in particular elafin (an elastase inhibitor) and ferritin, are considered to play roles in the DTH reaction. The other 18 fragments are probably derived from unknown genes. Cloning of the cDNAs of one of these genes indicated that it is that for guinea pig tryptophanyl-tRNA synthetase (WRS), a protein found to be induced by interferon-gamma and upregulated during the late stages of mononuclear phagocyte maturation in vitro. Strong induction of the WRS gene during the DTH reaction suggests its involvement in the in vivo immune response.     

IFN-gamma production by intrinsic renal cells and bone marrow-derived cells is required for full expression of crescentic glomerulonephritis in mice

The contribution of IFN-gamma from bone marrow (BM) and non-BM-derived cells to glomerular and cutaneous delayed-type hypersensitivity (DTH) was studied in mice. Chimeric IFN-gamma mice (IFN-gamma(+/+) BM chimera), in which IFN-gamma production was restricted to BM-derived cells, were created by transplanting normal C57BL/6 (wild-type (WT)) BM into irradiated IFN-gamma-deficient mice. BM IFN-gamma-deficient chimeric mice (IFN-gamma(-/-) BM chimera) were created by transplanting WT mice with IFN-gamma-deficient BM. WT and sham chimeric mice (WT mice transplanted with WT BM) developed crescentic glomerulonephritis (GN) with features of DTH (including glomerular T cell and macrophage infiltration) in response to an Ag planted in their glomeruli and skin DTH following subdermal Ag challenge. IFN-gamma-deficient mice showed significant protection from crescentic GN and reduced cutaneous DTH. IFN-gamma(+/+) BM chimeric and IFN-gamma(-/-) BM chimeric mice showed similar attenuation of crescentic GN as IFN-gamma-deficient mice, whereas cutaneous DTH was reduced only in IFN-gamma(-/-) BM chimeras. In crescentic GN, IFN-gamma was expressed by tubular cells and occasional glomerular cells and was colocalized with infiltrating CD8(+) T cells, but not with CD4(+) T cells or macrophages. Renal MHC class II expression was reduced in IFN-gamma(+/+) BM chimeric mice and was more severely reduced in IFN-gamma-deficient mice and IFN-gamma(-/-) BM chimeric mice. These studies show that IFN-gamma expression by both BM-derived cells and intrinsic renal cells is required for the development of crescentic GN, but IFN-gamma production by resident cells is not essential for the development of cutaneous DTH.     

Immunologic function during adjuvant BCG immunotherapy for malignant melanoma: Induction of anergy

Summary Serial tests of immunological function were performed on 28 patients participating in a randomized controlled clinical trial of adjuvant Tice-stain BCG immunotherapy administered by tine technique for malignant melanoma. Cryopreserved lymphocyte samples obtained prior to study entry and at 3 and 6 months there-after were tested by mixed lymphocyte culture (MLC), cell-mediated lympholysis (CML), antibody-dependent cell-mediated cytotoxicity (K cell), and natural killing (NK cell) assays, the last two assays being performed with the Chang cell line. Delayed-type hypersensitivity (DTH) skin tests to recall antigens were performed at the same intervals.At entry to the study in vitro lymphocyte reactivity of patients was similar to that of normal controls, and most (75%) of the patients reacted to at least one recall antigen. Serial lymphocyte reactivity measured by the in vitro tests was not different in the BCG and control groups, but BCG treatment was associated with a marked, statistically significant (P<0.01) reduction in DTH skin test reactivity. BCG therapy was not shown to delay recurrence of the disease.     

Activation of T cells by glutaraldehyde-fixed erythrocyte antigens: radiosensitivity of cells mediating delayed-type hypersensitivity reactions in the mouse.

Mice immunized with glutaraldehyde-fixed sheep red blood cells (G-SRBC) show delayed-type hypersensitivity (DTH) reactions to G-SRBC or SRBC. The specificity of the DTH reaction of mice sensitized with glutaraldehyde-fixed antigens is similar to that found after sensitization with unfixed antigens. The dose-response curve for sensitization by glutaraldehyde-fixed SRBC was very different from the curve for normal SRBC. At low doses, both antigens were effective in sensitizing to show DTH but neither induced an antibody response. However, at high antigen doses, only the glutaraldehyde-fixed antigen was efficient in sensitizing to show DTH and it failed to raise an antibody titer. Spleen cells of mice sensitized with fixed RBC can transfer DTH locally but if the donor cells are irradiated (500 R), the transfer is abrogated. In contrast, the transfer of DTH by spleen cells of mice immunized with unfixed antigen is not affected by 500 R. The transfer of DTH by spleen cells of mice immunized with fixed antigen can be blocked by “in vitro desensitization” while the transfer of DTH by spleen cells from mice primed with normal antigen is resistant to “in vitro desensitization.” These results suggest that immunization of mice with different physical states of the same antigen can result in the activation of antigen-specific T cells which exhibit markedly different properties.     

The relationship of abnormalities of cellular immunity to antibodies to HTLV-III in homosexual men

A comprehensive evaluation of the cellular immune system (total T-cell, helper cell, suppressor cell, and natural killer cell numbers; in vitro interleukin-2 production, T-cell responses to mitogens and antigens, serum beta 2 microglobulin levels, and delayed hypersensitivity skin tests) was performed on 36 HTLV-III seronegative and 16 HTLV-III seropositive healthy homosexual men, 48 asymptomatic homosexual men with the chronic lymphadenopathy syndrome, 41 patients with AIDS, and 29 heterosexual controls without any known risk factors for AIDS. Our studies demonstrate that HTLV-III seronegative homosexual men have normal cellular immunity and are comparable to heterosexual controls. The abnormalities of lymphocyte subsets observed in HTLV-III seropositive healthy homosexual men are comparable to subjects with chronic lymphadenopathy. Assays of lymphocyte function, with the exception of delayed type hypersensitivity (DTH) skin tests, are similar in each group except patients with AIDS. Subjects with chronic lymphadenopathy were less responsive to DTH skin tests and HTLV-III seropositive healthy homosexuals were comparable to chronic lymphadenopathy subjects. We conclude that immunologic abnormalities in homosexual men are attributable to infection with HTLV-III.