Differential effect of experimental diabetes on the early and late phase of contact sensitivity reaction in mice

Contact sensitization induces two different kinds of T cells (both Ly 1) that act in sequence to produce upon challenge with antigen a classical 24-hour local skin swelling reaction. One of these cells produces an antigen-specific factor. It has been suggested that it sensitizes mast cells, similar to IgE antibody, and causes them to release vasoactive amines in the presence of antigen. This results in an early (2-hour) swelling reaction. Increased vascular permeability facilitates the entry of the second, lymphokine-producing Ly 1 cell into the site of reaction to elicit the classical 24-hour delayed-type hypersensitivity reaction. In alloxan diabetic mice, contact sensitivity reactions are reduced significantly, and our experiments show that insulin deficiency affects only the activity of the late acting, lymphokine-producing cell and leaves the factor-producing cell responsible for the early swelling reaction unaffected. Our experiments demonstrate that insulin deficiency has different effects on distinct subpopulations of T lymphocytes.     

Identification and partial characterization of a T-cell-derived antigen-binding factor from mice infected with the intestinal helminth Trichinella spiralis

Immunochemical and biological characterization was performed of an antigen-binding factor derived from culture supernatants of T cells from mice infected 4 days previously with the intestinal helminth Trichinella spiralis. Affinity chromatography with T. spiralis antigen resulted in the purification of a protein, provisionally designated Trichinella factor (Tric-F), that shared antigenic and other properties with a known T-cell-derived antigen-binding factor of different antigenic specificity, picryl chloride factor, which mediates an early 2-hour component of contact sensitivity. Tric-F lacked determinants of immunoglobulins and possessed determinants shared by other antigen-specific T cell factors, as determined by ELISA and antibody affinity chromatography. Biological activity of Tric-F was assayed in vivo and in vitro. Mice injected intravenously with Tric-F developed an antigen-specific early 2-hour ear swelling response following local challenge with T. spiralis antigen. These results corresponded to delayed-type hypersensitivity responses in the ears of T. spiralis-infected mice that comprised early 2-hour and late classical 24-hour responses. In vitro, Tric-F induced serotonin release by mast cells in the presence of T. spiralis antigen. Mast cells sensitized with Tric-F formed rosettes with antigen-coated sheep erythrocytes. It is suggested that Tric-F, an antigen-binding molecule that is T-cell-derived, mediates the early 2-hour component of delayed-type hypersensitivity and is involved in the initiation and regulation of T-cell-mediated intestinal inflammation during a T. spiralis infection in mice.     

Schistosoma mansoni-specific rat T cell clones. II. Different effects of adult worm-specific T cell clones in immunocompetent and nude infected rats

The in vivo functional activities of two highly proliferating helper rat T cell clones (E23 and G5) specific for the excretory-secretory antigens of Schistosoma mansoni adult worms were investigated. When injected into infected immunocompetent rats, both clones increased the antibody response against the 30-40-kDa schistosomulum surface antigens, but failed to induce an immune protection. In contrast, when the same clones were injected into infected nude rats, a high degree of protection was obtained. In this latter case the absence of detectable specific antibody response, whether of IgE or IgG isotype, suggested that parasites were destroyed by an antibody-independent mechanism, i.e. macrophages activation by lymphokines. Indeed supernatants obtained from T cell clones specifically restimulated with schistosome antigens expressed a macrophage activated activity similar to interferon-gamma. Following incubation with these supernatants or with the active fractions, macrophages exhibited a significant schistosomulicidal activity and both clones were shown to transfer an antigen-specific delayed-type hypersensitivity reaction to normal rats. Taken together these results demonstrate that, depending on the immune status of the host, antigen-specific T cell clones can function differently and consequently that one function associated with one type of lymphokine could be favored.     

Antigen-specific T-cell factors induce isotype-like suppression of mast cell and eosinophil-rich T-cell-dependent inflammation in the intestine of mice infected with Trichinella spiralis

The recent identification of a T-cell-derived antigen-binding molecule (TABM), Trichinella spiralis factor (Tric-F), isolated from culture supernatants of lymphoid cells from mice infected with the intestinal helminth T. spiralis, has led to investigation of the ability of Tric-F to induce a T-cell-dependent feedback circuit that ultimately suppresses the production of other TABMs with similar (isotype-like) features. This form of regulation that has been identified in contact hypersensitivity and in delayed-type hypersensitivity (DTH) responses to tumor cells, was shown not to be antigen-specific but to be DTH-specific. Injection of mice with the TABM called picryl chloride factor (PCl-F) induced suppression of the production of DTH-initiating TABMs of other antigenic specificities. In this study, we report that intravenous injection of mice with Tric-F or PCl-F, 8 days before an oral infection with T. spiralis, induced suppressor cells that inhibited the T-cell-dependent influx into the gut of inflammatory cells, comprising mast cells and eosinophils. Similar results were obtained when the mice were skin sensitized with PCl 8 days prior to a T. spiralis infection, i.e. in a system where TABMs are known to be produced. The phenotype of these suppressor cells was Lyt-1-2+. This suppression preferentially affected the parasite-induced DTH-like response in the gut. In contrast, increased levels of IgA plasma cells in the gut, and worm expulsion were not affected by these treatments. In reciprocal experiments, intravenous injection of Tric-F, or PCl-F, or an oral infection with T. spiralis (that results in the production of TABMs) given 8 days before contact sensitizing mice with PCl, resulted in a suppression of elicitation of cutaneous DTH, as measured by ear swelling. In contrast, pretreatment with anti-dinitrophenyl IgE antibody did not interfere with intestinal inflammation to T. spiralis nor with DTH to PCl. Our results suggest that similar to cutaneous DTH, T. spiralis-specific T-cell factors are involved in the initiation and regulation of the DTH-like mast cell and eosinophil-rich intestinal inflammation that accompanies T. spiralis infections in the gut. Since both Tric-F and PCl-F induce suppression of cellular immune responses in vivo, independent of antigen specificity, it is concluded that Tric-F belongs to the same isotype of TABMs as PCl-F that therefore can be regulated by a non-antigen-specific, isotype-like, T-cell-dependent feedback mechanism.     

Different mechanisms of release of vasoactive amines by mast cells occur in T cell-dependent compared to IgE-dependent cutaneous hypersensitivity responses

It has recently been shown that the classical 24-48-h component of delayed-type hypersensitivity (DTH) in mice is preceded by an early 2-h component. This early component of DTH resembles IgE-dependent hypersensitivity reactions, but is mediated by an antigen-specific T cell factor that activates cutaneous mast cells (MC). In the current study of cutaneous hypersensitivity reactions, evidence is presented that serotonin and histamine are released from the granules of MC in IgE-dependent responses, but that T cell activation of MC induces preferential release of serotonin. In T cell-dependent reactions, it was found that serotonin was released under experimental conditions in which MC granules were depleted of serotonin, but catabolism of serotonin in the cytosol was prevented. This suggests that T cells induce differential release of serotonin from non-granule storage sites in MC, such as transport vesicles in the cytoplasm. Morphological observations of MC in IgE-dependent compared to T cell-dependent cutaneous reactions were consistent with this hypothesis. Exocytosis of granules characterized IgE activation and was not found in MC that were activated by T cells, which instead showed mild degranulation accompanied by numerous cytoplasmic vesicles.     

A delayed-type hypersensitivity reaction initiated by a single T lymphocyte

In vivo primed T cells injected into the footpad of naïve recipients elicit a typical delayed-type hypersensitivity (DTH) reaction in the presence of their specific antigen. Serial dilutions of primed T cell populations were used in order to score positive and negative transfers. The values for the footpad swelling obtained after these transfers followed a bimodal distribution. This clear bimodal distribution with no overlapping between positive and negative transfers suggested that a single cell initiates the DTH reaction. Limiting dilutions of cloned T cells transferred with their antigen allowed us to demonstrate that a single cell is able to transfer a specific DTH reaction.     

Helper and suppressor functions of human mononuclear cells depleted of antigen-binding T8+ cells.

We have utilized the antigen-binding function of a subset of T8+ cells to remove these cells in vitro from human peripheral blood mononuclear cells. This was carried out by treating the cells with streptococcal antigen (SA), monoclonal anti-SA antibody and complement. The concentration of SA binding to T8+ cells differs with the HLA-DR type of the cells: 1 ng SA binds to DRw6+ cells and elicits T helper activity, whereas 1000 ng SA elicits T suppressor activity, in an assay for antibody-forming cells. After depletion of the antigen-binding cells by the SA-specific complement-dependent killing technique, the helper function of the DRw6+ cells was lost but suppression was elicited not only by 1000 ng but also by 1 ng SA. Similarly, DRw6- cells which bind 1000 ng SA to elicit helper activity and 1 ng to elicit suppression, when depleted of the SA-binding cells, resulted in loss of helper activity but again, suppression could be elicited by both 1000 and 1 ng SA. We suggest that treatment of mononuclear cells with antigen, the specific antibody and complement removes the T8+ antigen-binding cells which present antigen to T helper cells and results in the loss of helper function. Suppressor function is however, not only retained with the original concentration of SA but also expressed with that required to elicit helper function in the untreated cells. These findings are consistent with our hypothesis that the antigen-binding and presenting T8+ cells also function as contrasuppressor cells. Thus, the T8+ subset of cells have a dual function, to present antigen and to activate T helper cell function, and to prevent suppressor cells from inhibiting the helper cells.     

Development of delayed-type hypersensitivity during Mycobacterium lepraemurium infection in mice.

Various preparations of Mycobacterium lepraemurium were used to elicit delayed-type hypersensitivity in the footpad of mice infected with this organism. With a sonicated preparation of the mycobacterium, a significant increase in footpad swelling was elicited in mice infected with M. lepraemurium 5 weeks previously, but not in BCG-infected animals or uninfected controls. This footpad reaction was shown to peak at 24 h and to be associated with an infiltration of mononuclear cells. The kinetics of footpad swelling, its association with lymphoproliferation, and its dependence on T lymphocytes were each examined. The results support the hypothesis that this is a delayed-type hypersensitivity reaction. The ability to transfer this reactivity to normal mice with cells but not serum offers further confirmation that this hypersensitivity is dependent on cell-mediated immunological mechanisms rather than humoral antibody. The relevance of this to the study of the immunological response of mice to murine leprosy is discussed.     

Antigen-specific suppressor factors produced by T cell hybridomas for delayed-type hypersensitivity.

This study describes the generation of T hybridoma lines which secret factors specifically suppressing delayed-type hypersensitivity (DTH) to sheep red blood cells (SRBC). AKR strain-derived T lymphoma BW 5147 cells were fused with spleen cells from mice primed with SRBC and containing antigen-specific T suppressor cells for DTH. Supernants from the derived hybridomas were tested for suppression of either expression of induction of DTH to SRBC. Six lines produced specific suppressor activity for the expression of DTH; 4 lines produced suppressor activity for the induction of DTH of which only one line was antigen-specific. These lines were passaged in normal AKR mice, and the serum obtained had activity up to 10(-4) dilution. The factor was effective across the H-2 barrier.     

Regulation of the IgE antibody response

The IgE synthesis is regulated by T cell derived IgE-binding factors in an isotype-specific manner. The IgE-potentiating and IgE-suppressive factors may share common structural genes; therefore, a common polypeptide chain and their biologic activities are determined by posttranslational glycosylation processes. Under the physiological conditions, the carbohydrate moieties in the IgE-binding factors formed by a subset of T cells are determined by the ratio between two T cell factors, i.e., glycosylation-enhancing factors and glycosylation-inhibiting factors (GIF), in their environment. GIF is an immunosuppressive lymphokine. Repeated injections of this lymphokine into antigen-primed mice facilitated the generation of antigen-specific suppressor T cells and suppressed both IgE and IgG antibody responses. This effect of GIF was reproduced in vitro. Activation of antigen-specific T cells by antigen-pulsed macrophages, followed by propagation of the antigen-activated T cells by interleukin 2 in the presence of GIF resulted in the generation of suppressor T cells which produced antigen-specific GIF upon antigenic stimulation. Some of the T cell hybridomas constructed from the antigen-specific suppressor T cells formed antigen-specific GIF upon antigenic stimulation. The antigen-specific GIF formed by the T cell hybridoma share several common properties with antigen-specific suppressive factor and suppressed the antibody response of syngeneic mice in a carrier-specific manner. The results obtained with mouse lymphocytes suggest a maneuver to suppress the IgE antibody formation to an allergen in atopic patients.     

Adoptive immunotherapy with IL-2 results in the loss of delayed-type hypersensitivity responses and the development of immediate hypersensitivity to recall antigens

Skin testing represents a direct method of assessing immune responses in vivo. Twenty-six patients with metastatic cancer of the lung, kidney, or melanoma were treated with adoptive transfers of autologous tumor-infiltrating or blood lymphocytes and continuous infusions of interleukin-2 (IL-2). Prior to therapy, cutaneous anergy to recall antigens was observed in 19 patients (73%), whereas 6 (27%) displayed normal delayed-type hypersensitivity (DTH) responses. When tested again at the end of therapy, DTH responses could not be elicited in any of the patients. Proliferative responses to skin test antigens, lectins, and IL-2 diminished progressively during therapy but returned to baseline values at 1 month. Unexpectedly, 14 of these patients (53%) developed immediate skin test responses to candida antigens and 5 (19%) to mumps antigens. These immediate responses were characterized by local erythema and induration that developed within minutes of injecting antigen. Biopsies displayed marked dermal edema and infiltration by eosinophils. Although serum IgE levels were not increased, immediate reactivity could be transferred by a heat-sensitive serum factor. The implications of this novel response are uncertain, and its development did not correlate directly with the anti-tumor effects of therapy. We conclude that adoptive immunotherapy with IL-2 produces a reduction in cutaneous DTH and diminished responses to mitogens while simultaneously promoting cutaneous allergy. We hypothesize that this may reflect diminished IL-2 production by antigen-specific helper T cells and that other lymphokines may promote these immediate hypersensitivity responses.     

Flt3 ligand enhances the immunogenicity of a gag-based HIV-1 vaccine

Liposomes and Flt3 ligand (Flt3L), a ligand for the fms-like tyrosine kinase receptor Flt3/ FLK2, can augment the immune response to an HIV peptide vaccine. The HGP-30 peptide used in these studies is a synthetic peptide that corresponds to a highly conserved region of HIV-1 p17 gag (amino acids 86-115). Mice were immunized with HGP-30 or HGP-30 conjugated to keyhole limpet hemocyanin (KLH) and delayed-type hypersensitivity (DTH) responses, antibody (IgG) amount and antigen-specific proliferative responses by spleen cells were used to monitor the immune response. Daily injections of Flt3L prior to HGP-30 administration enhanced significantly an antigen-specific lymphocyte proliferation response when compared with Flt3L, HGP-30 alone or HGP-30 containing liposomes. Intravenous administration of HGP-30 was superior to intramuscular (i.m.) immunization for the induction of DTH responses. The HGP-30/KLH containing liposomes enhanced both DTH and antibody responses, while liposomes containing HGP-30 peptide elicited only T cell responses. In these studies, either Flt3L or liposomes increased DTH responses compared with the i.m. injection of the HGP-30 vaccine alone.     

Pertussis toxin potentiates Th1 and Th2 responses to co-injected antigen: adjuvant action is associated with enhanced regulatory cytokine production and expression of the co-stimulatory molecules B7- 1, B7-2 and CD28

Pertussis toxin (PT) is a major virulence factor of Bordetella pertussis which exerts a range of effects on the immune system, including the enhancement of IgE, IgA and IgG production, delayed-type hypersensitivity reactions, and the induction of experimental autoimmune diseases. However, the mechanism by which PT mediates adjuvanticity remains to be defined. In this investigation we have shown that PT can potentiate antigen-specific T cell proliferation and the secretion of IFN-gamma, IL-2, IL-4 and IL-5 when injected with foreign antigens. A chemically detoxified PT and a genetic mutant with substitutions/deletions in the S-1 and B oligomer components that abrogate enzymatic and binding activity displayed no adjuvant properties. In contrast, a non-toxic S-1 mutant devoid of enzymatic activity but still capable of receptor binding retained its adjuvanticity, augmenting the activation of both Th1 and Th2 subpopulations of T cells. In an attempt to address the mechanism of T cell activation, we found that PT stimulated the production of IFN- gamma and IL-2 by naive T cells and IL-1 by macrophages. Therefore potentiation of distinct T cell subpopulations may have resulted in part from the positive influence of IFN-gamma on the development of Th1 cells and the co-stimulatory role of IL-1 for Th2 cells. Furthermore, PT augmented expression of the co-stimulatory molecules B7-1 and B7-2 on macrophages and B cells, and CD28 on T cells, suggesting that the adjuvant effect may also be associated with facilitation of the second signal required for maximal T cell activation. This study demonstrates that the immunopotentiating properties of PT are largely independent of ADP-ribosyltransferase activity, but are dependent on receptor binding activity and appear to involve enhanced activation of T cells.      

Suppressor T cells for delayed-type hypersensitivity to Japanese encephalitis virus.

The delayed-type hypersensitivity (DTH) to Japanese encephalitis virus (JEV) and the suppressor cells controlling it and the antibody-forming cells in inbred Swiss mice have been studied. JEV induces DTH, with a peak response at day 7 following infection which persists at low levels at least up to 119 days. Suppressor activity appeared on day 18. It was transferable by immune spleen cells. Treatment of spleen cells with anti-Thy-1.2 antisera and complement abrogated the suppressor activity. The homogenate of the spleen was equally effective in mediating suppression of DTH and the humoral response as measured by direct antibody plaque-forming cell (IgM-PFC) assay. The suppressor activity was antigen-specific both on DTH and T helper for antibody response as the immune responses against SRBC or Coxsackie B4 virus were not suppressed. The suppressor cells were sensitive to cyclophosphamide treatment when the drug was given 48 hr before their appearance. It is, therefore, concluded that in JEV infection of mice, antigen-specific suppressor T cells are generated, both for DTH and IgM antibody, which are cyclophosphamide-sensitive and mediate suppression through soluble product(s).     

Antigen-specific augmentation factor involved in murine delayed-type footpad reaction. III. Genetic restriction of delayed hypersensitivity augmentation factor (DAF)

We found an antigen-specific factor capable of augmenting delayed-type hypersensitivity (DTH) in the culture supernatant of the mixture of immune T cells and specific antigen, or in the serum of mice immunized with xenogeneic erythrocytes and elicited for DTH footpad reaction. Previous experiments on the genetic restriction of this factor (DTH-augmentation factor; DAF) indicated that DAF activity was effective across the MHC-barrier in C3H/He (H-2k)--BALB/c (H-2d) system. The genetic restriction between DAF and its acceptor cells was then investigated precisely using Igh (immunoglobulin heavy chain locus)-congeneic mice: 1) Expression of DAF activity was MHC-nonrestricted, 2) but was restricted by the Igh-linked gene on the 12th chromosome, 3) such Igh-linked gene restriction was also demonstrated by an absorption test with normal spleen cells. The acceptor cells for DAF were Thy-1+,L3T4+,Lyt-2- T cells.     

Deletion,but not anergy,is involved in TGF-beta-treated antigen-presenting cell-induced tolerance

Intravenous injection of transforming growth factor (TGF-)-beta-treated antigen-presenting cells (APC) pulsed with antigen induces antigen-specific tolerance in both naive and previously primed mice. Although TGF-beta-treated APC-induced tolerance is associated with induction of regulatory T cells and impaired delayed-type hypersensitivity (DTH) responses, the specific mechanisms that mediate this tolerance are not currently known. The goal of the present report was to study the mechanisms involved in TGF-beta-treated APC-induced tolerance by determining the fate of the antigen-specific effector T cells that are regulated. Using a well-characterized system that allows tracking of small numbers of TCR transgenic T cells, we have found that antigen-specific T cell expansion, either in vivo or in vitro, is inhibited in mice that have been injected with TGF-beta-treated APC. The failure of antigen-specific effector T cells to expand did not appear to be due to the induction of anergy, since carboxyfluorescein diacetate succinimidyl ester (CFSE)-labeled cells divided normally in response to antigen and adjuvant in vivo, and addition of exogenous IL-2 was unable to restore T cell expansion in in vitro assays. Interestingly, the percentage of CFSE-labeled cells was decreased after >7-8 divisions following culture in vitro, which correlated with a significant increase in cell death. Cell death was prevented and the ability to expand in vitro was restored by treatment with anti-Fas ligand (FasL) antibody. In conclusion, tolerance induced by TGF-beta-treated APC appears to be associated with deletion of antigen-specific T cells involving the Fas-FasL pathway.     

Differential ability of occupational chemical contact and respiratory allergens to cause immediate and delayed dermal hypersensitivity reactions in mice.

Trimellitic anhydride (TMA) is known to cause occupational respiratory allergy associated with the presence of specific IgE antibody. Other chemicals, such as 2,4-dinitrochlorobenzene (DNCB), while exhibiting a clear potential for contact sensitization, apparently lack the ability to induce respiratory allergy in man. It has been shown previously that although both chemicals are immunogenic in mice, each provoking contact sensitization, exposure only to TMA results in an IgE antibody response. In the present study, to examine further the characteristics of human allergens, we have compared the ability of TMA and DNCB to elicit immediate and delayed cutaneous hypersensitivity reactions in mice. Topical exposure to both chemicals resulted in delayed (24 h) hypersensitivity. However, only TMA induced, in addition, an immediate (1 h) dermal reaction following local challenge. Serum from TMA-immune mice, but not from untreated mice or mice sensitized with DNCB, was able to transfer immediate hypersensitivity to naive recipients. The kinetics of passive sensitization with TMA-immune serum, together with the fact that immediate hypersensitivity to DNCB could be induced with monoclonal IgE anti-dinitrophenol (DNP) antibody, suggests that the immediate dermal responses caused by TMA are effected by hapten-specific IgE. These data demonstrate that different classes of occupational chemical allergen exhibit a variable potential to elicit immediate and delayed dermal hypersensitivity reactions in mice, and provide a novel approach to the classification and characterization of human allergens.     

T cell-replacing factor in specific antibody responses to influenza virus by human blood B cells

In man, B cell maturation factors obtained from T cells or T cell lines have been shown to induce antibody formation in mitogen or anti-immunoglobulin activated B cells, and in some continuous B cell lines, but the relationships between these factors and B cell differentiation factors in antigen-specific antibody responses is unclear. We have now shown that supernatants from phytohemagglutinin-activated tonsil cells, or from the Gibbon Ape T cell line MLA-144, can substitute for T cells in the specific antibody response by human blood B cells to influenza virus. Thus, T cell-depleted non-rosette-forming (E-) cells prepared from peripheral blood mononuclear cells made antibody when cultured with antigen and factor together, whereas control cultures of E- cells with either antigen or factor alone did not. Moreover, E- cells cultured with factor and influenza virus strain A/X31 made antibody to A/X31, but not the non-cross-reacting strain, B/HK (and vice versa) showing that the response was antigen specific. The activity in these supernatants, therefore, fulfilled the functional definition of T cell-replacing factor (TRF). The possibility that interleukin 2 (IL 2) present in the TRF-containing supernatants was expanding residual T cells in the E- preparations to provide normal T cell help was excluded in three different ways. First, E- cells depleted of T (Leu4+) cells to undetectable levels made normal amounts of antibody when cultured with antigen and TRF. Secondly, a limiting dilution technique was employed to show that help in cultures of E- cells and TRF was not mediated by antigen-specific T helper cells. Thirdly, TRF-containing supernatants depleted of IL2 retained activity, whereas purified IL2 was inactive. Preliminary purification of TRF by gel filtration on Ultrogel AcA54 columns showed that all the activity eluted in a single peak between 35 000 and 43 000 molecular weight. This distinguishes human TRF from IL 2 and from other B cell maturation factors with a molecular weight range of 15 000-20 000 which act on continuous B cell lines. In addition to TRF, supernatants from phytohemagglutinin-activated tonsils also contained a factor which could induce polyspecific IgM production, but only in cultures containing significant numbers of T cells. This additional activity may have been due to IL 2, and provides an explanation for the apparent T cell-dependent effects sometimes observed in experiments designed to test B cell differentiation factors on T cell-depleted normal B cells.     

Induction of antigen-specific suppression by circulating Cryptococcus neoformans antigen.

Immunoaffinity chromatography of sera from mice infected with Cryptococcus neoformans (Inf-MS) on a column with rabbit anti-cryptococcal antibody as the ligand resulted in the adsorption of the component(s) that induce suppression of the cryptococcal delayed-type hypersensitivity (DTH) response. In contrast, immunoaffinity chromatography of Inf-MS on columns coupled with cryptococcal antigen or goat anti-mouse IgM, IgG, and IgA did not adsorb the suppressive component(s). Quantification of cryptococcal antigen and anti-cryptococcal antibody in Inf-MS and column fractions established a direct correlation between cryptococcal antigen levels and suppressive activity; no correlation was observed between anti-cryptococcal antibody levels and suppressive activity. The suppression induced by Inf-MS was shown to be specific in that suppressive sera did not affect the induction of DTH responses to Listeria monocytogenes or dinitrofluorobenzene. These collective results provide evidence that cryptococcal antigen is the component in Inf-MS that induces antigen-specific suppression of the cell-mediated immune response to C. neoformans.     

Immune response potential of mast cell-deficient W/Wv mice

Immune responses of mast cell-deficient WBB6F1-W/Wv mice and their mast cell-sufficient littermates (LM: WBB6F1-W/+, Wv/+ and +/+) were compared. After a single intravenous injection of sheep erythrocytes (SE), polyvinylpyrrolidone or bacterial lipopolysaccharide, the antigen-specific IgM plaque-forming cell (PFC) response of W/Wv mice was similar to or greater than the response of LM mice. When both primary and secondary injections of SE or chicken gamma-globulin were given to mice and antigen-specific IgG PFC responses quantified, the response of W/Wv again was similar to or greater than that of LM mice. Serum titers of antigen-specific IgE were higher in W/Wv than in LM mice after injections of ovalbumin in alum or infections of Nippostrongylus brasiliensis. Ovalbumin-sensitized W/Wv and LM mice developed active systemic anaphylaxis after ovalbumin challenge. The ability of W/Wv mice to be sensitized for and elicit contact sensitivity (CS) reactions was studied using picryl chloride or dinitrofluorobenzene as sensitizing and challenge agents and quantifying 24-hour reactions by change in ear thickness. SE or methylated bovine serum albumin was used to sensitize and challenge mice for delayed-type hypersensitivity (DTH) reactions which were quantified at 24 h by change in foot pad or ear thickness. CS and DTH reactions of W/Wv and LM mice were similar. No evidence of immune deficiency of W/Wv mice was found.