Cure of murine candidiasis by recombinant soluble interleukin-4 receptor

Neutralization of interleukin (IL)-4 by specific antibody exerts therapeutic activity in a murine model of systemic candidiasis characterized by strong T helper type 2 (Th2) responses. To investigate whether recombinant soluble IL-4 receptor (sIL-4R) could be used to block IL-4 action in vivo, mice treated with pharmacologic doses of sIL-4R at the time of infection were examined for progression of disease, development of footpad responses, serum IgE levels, and cytokine production in vitro by CD4+ lymphocytes. Following sIL-4R treatment, persistent ablation of circulating IL-4 detected by ELISA was associated with a cure rate of > 90% in otherwise lethally infected mice, onset of durable protection, and a shift from a predominant Th2 to a Th1 pattern of reactivity. In addition, when administered to genetically susceptible adult mice with gastrointestinal yeast colonization, the sIL-4R stimulated Th1-associated anticandidal resistance.

Neutralization of IL-10 up-regulates nitric oxide production and protects susceptible mice from challenge with Candida albicans

In contrast to several inbred strains of mice that develop Th1-associated anticandidal protection, DBA/2 mice are highly susceptible to systemic infection with Candida albicans cells of the attenuated variant PCA-2, and fatal outcome is observed in concurrence with sustained CD4+ cell production in vitro of IL-4 and IL-10. These Th2 cytokines were previously shown to inhibit nitric oxide (NO) production and yeast killing by activated macrophage cultures. We now show that macrophages from DBA/2 mice, either intact or infected with PCA-2, have lower capacity than resistant strains to synthesize NO in response to IFN-gamma. However, when treated with anti-IL-10 Abs at the time of infection, DBA/2 mice survived challenge and displayed increased production of NO in vitro after IFN-gamma activation. Cure was associated with the onset of footpad responses and durable protection, and higher frequencies of IFN-gamma-secreting cells were found in splenic CD4+ lymphocytes that expressed lower levels of IL-4 and IL-10 mRNA. Therefore, in DBA/2 mice, IL-10 contributes significantly to the selection of a Th2 response and lethality after PCA-2 challenge. An IL-10-induced defect in the activation and/or expansion of IFN-gamma-producing Th1 cells, IL-10 suppression of yeast killing, and the relative inability of DBA/2 macrophages to produce adequate levels of candidacidal NO may all contribute to the abnormal susceptibility of these mice to candidiasis.

Interleukin-12 but not interferon-gamma production correlates with induction of T helper type-1 phenotype in murine candidiasis

By means of polymerase chain reaction-assisted mRNA amplification, we have monitored message levels of interleukin (IL)-12 in splenic macrophages and of interferon-gamma (IFN-gamma), IL-4, and IL-10 in CD4+ and CD8+ T cells using Candida albicans/host combinations that result either in a T helper type-1 (Th1)-associated self-limiting infection ("healer mice") or in a Th2-associated progressive disease ("nonhealer mice"). The timing and pattern of message detection did not differ qualitatively by the expression of IFN-gamma or IL-10 mRNA in CD4+ and CD8+ cells from healer (i.e. PCA-2 into CD2F1) vs. nonhealer (i.e. CA-6 into CD2F1 or PCA-2 into DBA/2) mice. In contrast, IL-4 mRNA was uniquely expressed by CD4+ cells from nonhealer animals. IL-12p40 was readily detected in macrophages from healer mice but was detected only early in infection in mice with progressive disease. Cytokine levels were measured in sera, and antigen-driven cytokine production by CD4+ and CD8+ cells was assessed in vitro, while IFN-gamma-producing cells were enumerated in CD4- CD8- cell fractions. Overall, our results showed that (i) antigen-specific secretion of IFN-gamma protein in vitro by CD4+ cells occurred only in healing infection; (ii) IL-4- and IL-10-producing CD4+ cells would expand in nonhealer mice in the face of high levels of circulating IFN-gamma, likely released by CD4- CD8- lymphocytes; (iii) a finely regulated IFN-gamma production correlated in the healer mice with IL-12 mRNA detection, and IL-12 was required in vitro for yeast-induced development of IFN-gamma-producing CD4+ cells. Although the mutually exclusive production of IL-4/IL-10 and IFN-gamma by early CD4+ cells may be the major discriminative factor of cure and noncure responses in candidiasis, IL-12 rather than IFN-gamma production may be an indicator of Th1 differentiation.

Neutralization of IL-10 up-regulates nitric oxide production and protects susceptible mice from challenge with Candida albicans

In contrast to several inbred strains of mice that develop Th1-associated anticandidal protection, DBA/2 mice are highly susceptible to systemic infection with Candida albicans cells of the attenuated variant PCA-2, and fatal outcome is observed in concurrence with sustained CD4+ cell production in vitro of IL-4 and IL-10. These Th2 cytokines were previously shown to inhibit nitric oxide (NO) production and yeast killing by activated macrophage cultures. We now show that macrophages from DBA/2 mice, either intact or infected with PCA-2, have lower capacity than resistant strains to synthesize NO in response to IFN-gamma. However, when treated with anti-IL-10 Abs at the time of infection, DBA/2 mice survived challenge and displayed increased production of NO in vitro after IFN-gamma activation. Cure was associated with the onset of footpad responses and durable protection, and higher frequencies of IFN-gamma-secreting cells were found in splenic CD4+ lymphocytes that expressed lower levels of IL-4 and IL-10 mRNA. Therefore, in DBA/2 mice, IL-10 contributes significantly to the selection of a Th2 response and lethality after PCA-2 challenge. An IL-10-induced defect in the activation and/or expansion of IFN-gamma-producing Th1 cells, IL-10 suppression of yeast killing, and the relative inability of DBA/2 macrophages to produce adequate levels of candidacidal NO may all contribute to the abnormal susceptibility of these mice to candidiasis.

Mucosal and systemic T helper cell function after intragastric colonization of adult mice with Candida albicans

In 85% of adult DBA/2 mice inoculated intragastrically with Candida albicans, significant numbers of yeast cells were recovered from the gastrointestinal tract for up to 4 weeks, with the animals eventually clearing infection in the absence of systemic disease despite the occurrence of localized, self-limiting foci of mucosal involvement in their stomachs. Two major findings in colonized mice were defective production of IgA, interleukin (IL)-4, and IL-5 by Peyer's patches lymphocytes and increased numbers of interferon-gamma-producing T cells in mesenteric lymph nodes and spleens. Relatively low levels of circulating antibodies of T helper type 2 (Th2)-dependent isotypes were also found in colonized mice, which exhibited strong footpad responses and increased resistance to systemic reinfection. Unlike systemic challenge, gastrointestinal colonization of adult immunocompetent DBA/2 mice with C. albicans appears to be an effective stimulus for the systemic development of protective Th1 responses.

Natural killer cells do not play a dominant role in CD4+ subset differentiation in Candida albicans-infected mice

The effects of in vivo administration of monoclonal antibodies against NK-1.1-bearing cells on the early production of gamma interferon (IFN-gamma) in vitro and development of Th1-associated immunity were studied in mice infected with a live vaccine strain of Candida albicans. At 1 and 4 days postinfection, natural killer (NK) cell-enriched fractions from the spleens of antibody-treated mice displayed a dramatic reduction in 5E6+ lymphocytes and negligible anti-YAC-1 cytotoxic activity in vitro. Nevertheless, the frequency of IFN-gamma-producing cells in those fractions was reduced by less than half, on average, by anti-NK-1.1 treatment in vivo. In addition, the antibody-treated and infected mice demonstrated unchanged T helper cell responses, as measured by yeast-specific footpad reactions, resistance to reinfection, occurrence of antibodies of different isotypes, and production in vitro of interleukin-2 (IL-2), IFN-gamma, IL-4, and IL-10 by CD4+ cells. Therefore, although NK cells may contribute to early IFN-gamma production in Candida-vaccinated mice, these cells apparently do not play a dominant role in the qualitative development of yeast-specific T helper responses.

Low-dose streptozotocin-induced diabetes in mice. II. Susceptibility to Candida albicans infection correlates with the induction of a biased Th2-like antifungal response

We have previously found that the development of fatal disseminated candidiasis correlates with the detection of a strong Th2 response, while protective antifungal immunity is associated with a predominant Th1 response. In the present study we verified the hypothesis that an altered antifungal Th response could be responsible for the high susceptibility of diabetic mice to systemic Candida albicans infection. Outbred CD1 mice rendered diabetic with multiple low doses of the pancreatic islet beta-cell toxic, streptozotocin, develop a fatal systemic infection when injected with low-virulence C. albicans cells. Progressive disease was found to be associated with the presence in the serum of IgA, IgE, and IgG1 Candida-reactive specific antibodies, absent footpad reactions, and elevated production in vitro of the Th2 cytokines IL-4, IL-6, and IL-10 but not the Th1 cytokine IFN-gamma. Both the Th2 and Th1 (IL-2 and IFN-gamma) cytokines were produced in vitro by CD4+ lymphocytes from noninfected diabetic mice that, in addition, showed a noticeable footpad reaction to Candida antigens. Thus, it appears that a perturbation in the anticandidal T helper responses resulting in the induction of a biased Th2-like antifungal response renders diabetic mice highly susceptible to systemic C. albicans infection.

Raven's colored progressive matrices: a normative study of a random sample of healthy adults

Raven's Colored Progressive Matrices Test (RCPM) was administered to 894 normal healthy adults who were randomly selected in six Italian cities and in the Republic of San Marino. Gender, age, and education significantly influenced overall test performance, and performance on different RCPM subsets. Findings from this large random sample provide demographic corrections to test scores for use in clinical practice.

Interleukin-4 and interleukin-10 inhibit nitric oxide-dependent macrophage killing of Candida albicans

Mouse peritoneal and splenic macrophages treated with interferon-gamma (IFN-gamma) and infected with the yeast Candida albicans expressed high fungicidal activity in vitro that correlated with increased nitrite concentrations in culture supernatants. Both effects were reduced by an inhibitor of nitric oxide (NO) synthesis which, in vivo, impaired the animals' ability to mount a footpad reaction and clear the fungus from infected organs. Because T helper type-2 (Th2) cytokines in candidiasis are known to limit the expression of protective Th1 functions, we tested the effect of interleukin (IL)-4 and IL-10 on candidacidal activity and NO production of IFN-gamma-activated macrophages. Fungal killing and NO secretion were inhibited, in a dose-dependent manner, by the two cytokines either separately or in combination. Impaired candidacidal activity was also demonstrable in the presence of monoiodoacetic acid, an inhibitor of phagocytosis. These data demonstrate that NO is involved in macrophage killing of C. albicans and support the notion that regulation of Th1 effector function by IL-4 and IL-10 might involve modulation of NO synthesis.

CD4+ subset expression in murine candidiasis. Th responses correlate directly with genetically determined susceptibility or vaccine-induced resistance

Previous work has shown that in hybrid (BALB/cCr x DBA/2Cr)F1 mice the development of a fatal disseminated disease by systemic infection with virulent Candida albicans is associated with the detection of strong Th2-like responses. However, a predominant Th1-like response and long-lived antifungal protection are induced by vaccinating these mice with live blastospores of attenuated C. albicans strains. When injected into DBA/2Cr mice, one such live vaccine strain was found in the present study to result in a progressive disease characterized by strong Th2 responses. Elevated serum IgG1, IgA, and IgE responses, weak or absent footpad reactions, sustained production in vitro of Th2 (IL-4 and IL-10) but not Th1 (IL-2 and IFN-gamma) cytokines by CD4+ cells, and eosinophilia were all detected in DBA/2 mice after infection with the attenuated vaccine. This was in marked contrast with the development of strong Th1 responses and persistent anticandidal protection in similarly infected, H-2-compatible BALB/cCr mice. Therefore, our data suggest that the type of Th response that predominates in mice after C. albicans infection correlates with genetically determined susceptibility or vaccine-induced resistance. Moreover, the genetic control of this resistance may not be associated with the H-2 complex.

CD4+ subset expression in murine candidiasis. Th responses correlate directly with genetically determined susceptibility or vaccine-induced resistance

Previous work has shown that in hybrid (BALB/cCr x DBA/2Cr)F1 mice the development of a fatal disseminated disease by systemic infection with virulent Candida albicans is associated with the detection of strong Th2-like responses. However, a predominant Th1-like response and long-lived antifungal protection are induced by vaccinating these mice with live blastospores of attenuated C. albicans strains. When injected into DBA/2Cr mice, one such live vaccine strain was found in the present study to result in a progressive disease characterized by strong Th2 responses. Elevated serum IgG1, IgA, and IgE responses, weak or absent footpad reactions, sustained production in vitro of Th2 (IL-4 and IL-10) but not Th1 (IL-2 and IFN-gamma) cytokines by CD4+ cells, and eosinophilia were all detected in DBA/2 mice after infection with the attenuated vaccine. This was in marked contrast with the development of strong Th1 responses and persistent anticandidal protection in similarly infected, H-2-compatible BALB/cCr mice. Therefore, our data suggest that the type of Th response that predominates in mice after C. albicans infection correlates with genetically determined susceptibility or vaccine-induced resistance. Moreover, the genetic control of this resistance may not be associated with the H-2 complex.

Course of Primary Candidiasis in T Cell-Depleted Mice Infected with Attenuated Variant Cells

Anti-CD4, anti-CD8, or anti-interferon-gamma (IFN-gamma) antibodies or combinations of them were administered in the early stages of chronic infection of mice with a Candida albicans live vaccine strain, and the animals were monitored for course of primary infection, development of delayed-type hypersensitivity, resistance to reinfection, production of interleukin 2 (IL-2) and IFN-gamma in vitro by splenic lymphocytes, and levels of IL-2 and IFN-gamma transcripts in these cells. CD4+ cell and IFN-gamma depletion resulted in the development of fatal candidiasis by the attenuated yeast vaccine. In contrast, either treatment alone modified the course but not the outcome of primary infection, though each prevented the development of resistance to reinfection. Our data thus indicate that both IFN-gamma and CD4+ cells participate in resistance to primary infection with attenuated yeast cells and are critical in the induction of persistent systemic anticandidal immunity.

Gamma interferon modifies CD4+ subset expression in murine candidiasis

A single injection of monoclonal antibody to gamma interferon administered in conjunction with a live Candida albicans yeast cell vaccine resulted in the detection of nonprotective Th2 rather than protective Th1 responses and altered the early expression of interleukin 4 and gamma interferon mRNA in CD4+ cells.

Drug-induced modulation of IL-2 production in experimental murine trypanosomiasis

In this study we evaluated the effects of N-acetyl-cysteine and indomethacin in restoring IL-2 producing ability in vitro of splenocytes from mice infected with Trypanosoma equiperdum. Spleen cells from these mice were found to produce significantly lower levels of interleukin-2 (IL-2) in response to mitogen stimulation than spleen cells from uninfected control mice. This was accompanied by considerable suppression of IL-2-receptor expression, which was not attributable to the elimination of a particular T-cell subset. Impairment of IL-2 production was not due to a primary defect in L3T4+ T-cells, but rather to the presence of both adherent and non-adherent suppressor cells that apparently acted via prostaglandin-independent and dependent mechanisms. In fact, the IL-2-producing ability of lymphocytes from infected mice could be efficiently restored by in vitro exposure to N-acetyl-cysteine or indomethacin.

Immunogenic tumor variants induced by drug treatment of the L5178Y lymphoma: search for serologically defined antigens at the clonal level

Highly immunogenic tumor variants are generated by in vitro or in vivo treatment of the murine L5178Y lymphoma line with triazene derivatives. Most of these variants express new transplantation- and antibody-defined antigens that previous studies have shown to be closely related. One such 80-kDa protein on the surface of clone-D cells was found to be related to xenotropic MuLV gp70 molecules. To investigate the possible relevance of clone-D data to general properties of immunogenic variants in this tumor model system, polyclonal syngeneic antisera raised to a panel of immunogenic clones (including clone D) of the drug-treated L5178Y lymphoma line were employed in the immunoprecipitation of cell-surface and intrinsically labeled variant cells. In all clones, 1- and 2-dimensional electrophoretic analysis of the immunoprecipitates detected an antigen of approximately 80 kDa, and 35S-labeled 80-kDa molecules could be cross-precipitated from all clones by the panel of clone-specific antisera. In addition, 45- and 30-kDa components were also found in metabolically labeled variant cells. While the surface 80-kDa component was reactive with anti-xenotropic gp70 antibodies, the 30-kDa molecule was removed by anti-gag p30 antibody in sequential immunoprecipitation experiments. These data suggest that expression of aberrant, retrovirus-related proteins is a common finding in immunogenic cells of the drug-treated L5178Y lymphoma line.

Involvement of the Th1 subset of CD4+ T cells in acquired immunity to mouse infection with Trypanosoma equiperdum

Heat- or merthiolate-inactivated Trypanosoma equiperdum was administered to recipient mice that were subsequently challenged with viable inocula of the same stabilate. Only mice inoculated with merthiolate-killed parasites were completely protected from a challenge inoculum of 10(3) trypanosomes, an effect that was abolished by prior immunosuppression of mice. Immune sera from protected animals contained high levels of interferon (IFN)-gamma and specific IgG2a antibodies. Spleen cells from these mice produced high amounts of interleukin (IL)-2 and IFN-gamma in vitro in response to specific antigen or concanavalin A, whereas splenocytes from mice receiving heat-killed parasites produced high amounts of IL-6. In contrast, the production of tumor necrosis factor (TNF)-alpha and colony-stimulating activity (CSA) was not significantly different in mice receiving either killed parasite preparation. The protection in immunized mice was associated with the detection of strong delayed-type hypersensitivity (DTH) to T. equiperdum antigens, an effect that could be adoptively transferred onto naive recipients by specifically immune CD4+ lymphocytes. These results suggest that the development of protective immunity in mice to T. equiperdum by our immunization protocol may involve the activity of helper/DTH T cells, particularly those of the Th1 subset.

Tumor-specific L3T4+ and Lyt-2+ lymphocytes in mice primed to mutagenized cell variants

We have investigated the tumor-specific reactivity of different T-cell subsets from mice primed with clonal variants of L5178Y and P815 cells treated with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). In both tumor systems, anti-parental tumor immunity and protection against non-immunogenic clones were only induced by vaccinating the hosts with highly immunogenic cell variants, and the effect correlated with the detection of TATA-specific delayed-type hypersensitivity (DTH) reactions. The footpad reaction was transferable with spleen cell populations from immunized mice, and enrichment of splenic lymphocytes in L3T4+ but not Lyt-2+ lymphocytes increased the footpad swelling. Unfractionated spleen cell populations from immunized mice released high amounts of IL-2 and IFN-gamma in vitro in response to parental antigens. Purified L3T4+ and Lyt-2+ lymphocytes also produced IFN-gamma when incubated in vitro with the parental tumors and accessory cells. It is suggested that the mechanisms of anti-parental tumor immunity induced by MNNG-treated variants may be similar to those described previously for triazene-xenogenized L5178Y/DTIC cells, and may involve induction of a tumor-specific DTH reaction and IFN-gamma-mediated stimulation of non-specific tumoricidal effects.

Neutralizing antibody to interleukin 4 induces systemic protection and T helper type 1-associated immunity in murine candidiasis

An interleukin 4 (IL-4)-specific monoclonal antibody (mAb) was administered to mice infected systemically with the yeast Candida albicans, and the animals were monitored for mortality, development of delayed-type hypersensitivity, production of antibodies of different isotypes, release of IL-2, IL-4, IL-6, and interferon gamma (IFN-gamma) in vitro by splenic CD4+ lymphocytes, and levels of IL-4 and IFN-gamma mRNA in these cells. Neutralization of IL-4 by three weekly injections of mAb in several independent experiments resulted in an overall cure rate of 81% versus 0% of controls. Cure was associated with efficient clearance of the yeast from infected organs and histologic evidence of disease resolution, detection of strong T helper type 1 (Th1) responses, and establishment of long-lasting protective immunity. Soon after infection, and as a result of the first or second injection of mAb, there was a decrease in IL-4 mRNA in CD4+ cells, which was accompanied by an increase in the levels of IFN-gamma-specific transcripts. Our data thus indicate that the production of IL-4 by Th2 cells may limit Th1-associated protective immunity in murine candidiasis.

Antigen-specific cytolysis of infected cells in murine candidiasis

Immune L3T4+ and Lyt-2+ lymphocytes play an important role in the acquired resistance of mice to challenge with virulent Candida albicans, and release macrophage-activating cytokines in response to yeast cells in vitro. To determine whether antigen (Ag)-specific cytotoxic T lymphocytes are generated during fungal infection, purified L3T4+ and Lyt-2+ lymphocytes from immunized mice were cultured in the presence of syngeneic accessory cells, Candida Ag, and IL-2. Yeast-infected bone marrow macrophages and peritoneal exudate neutrophils were used as target cells in a standard 51Cr release assay. Ag-specific, MHC-unrestricted lysis of infected macrophages was evident with immune Lyt-2+ cells after 5-10 days in culture. Under the same experimental conditions, the cytotoxic activity of L3T4+ cells was negligible, but its expression could be induced by the addition of anti-CD3 antibody. Culturing immune Lyt-2+ cells for shorter periods of time (1-2 days) resulted in preferential lysis of infected neutrophils. In addition, at limiting effector cell numbers, Ag-specific MHC-restricted lymphocytes with cytotoxic activity to infected macrophages could be identified. We suggest that C. albicans infection stimulates multiple cytotoxic T-cell precursors with varying recognition stringency, which may have an important role in antifungal resistance in vivo.

O6-methylguanine-DNA methyltransferase activity and induction of novel immunogenicity in murine tumor cells treated with methylating agents

To investigate the mechanism of the generation of immunogenic tumor variants by mutagenic drugs, murine leukemia cells exhibiting different sensitivity to killing by the alkylator 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) and different ability to repair O6-methyl-guanine in their DNA were treated in vitro with a series of methylating agents, including triazene derivatives, temozolomide, and streptozotocin. At the population level, we found that BCNU-resistant cells (L1210/BCNU) that appeared to be cross-resistant to killing by a dimethyltriazene and expressed high levels of O6-methylguanine-DNA methyltransferase activity (mer+ phenotype) failed to generate highly immunogenic variant sublines on repeated exposure to the methylating agents. In contrast, all cells (L1210) that were susceptible to DNA alkylation damage and deficient in O6-methylguanine repair (mer-) developed immunogenic variant sublines. A noticeable exception was represented by streptozotocin treatment, which was equally effective in mer+ and mer- cells. At the clonal level, a single exposure to streptozotocin or a triazene derivative resulted in a high incidence (33% and 50%, respectively) of immunogenic cell generation in mer- cells only. In mer+ cells, streptozotocin treatment led to a 33% incidence of immunogenic clones only when the cells were concurrently exposed to O6-methylguanine as a free base. The activity of O6-methylguanine-DNA methyltransferase in mer+ cells was greatly reduced by treatment with O6-methylguanine or streptozotocin, and the combination of the two drugs led to enzyme levels similar to those observed in mer- cells. Taken together, these data suggest that the mechanism of O6-alkylation may be operative in the induction of novel tumor-cell antigenicity by methylating agents.

Th1 and Th2 cytokine secretion patterns in murine candidiasis: association of Th1 responses with acquired resistance

Two chemically mutagenized agerminative variants of Candida albicans were used to immunize mice against challenge with highly virulent cells of the parent strain. Although both mutants (Vir- 3 and Vir- 13) resulted in nonlethal infection and could be recovered from mouse organs for many days after the intravenous inoculation of 10(7) to 10(6) cells, significant protection to systemic challenge with virulent C. albicans was induced by only one (Vir- 3) of the two variants. Anticandidal resistance in Vir- 3-infected mice was associated with the occurrence in vivo of strong delayed-type hypersensitivity to Candida antigen, detection in vitro of highly fungicidal effector macrophages, and presence in the serum of a large proportion of Candida-reactive antibodies of the immunoglobulin G2a isotype. Bulk cultures of purified CD4+ lymphocytes from mice infected with either mutant were compared for their ability to produce gamma interferon (IFN-gamma), interleukin-2 (IL-2), IL-4, and IL-6 in vitro. After stimulation with specific antigen, CD4+ cells from Vir- 3-immunized mice released large amounts of the Th1-specific cytokines, IFN-gamma and IL-2, at a time when CD4+ cells from Vir- 13-infected mice predominantly secreted the characteristic Th2 cytokines, IL-4 and IL-6. These results were confirmed by quantitative analysis of cytokine-producing Th1 and Th2 cells. In addition, only mice infected with Vir- 3 displayed a high frequency of CD8+ cells with the potential for in vitro lysis of yeast-primed bone marrow macrophages. Purified CD4+ cells from Vir- 3-infected mice, but not a mixture of these cells with CD4+ lymphocytes from mice infected with Vir- 13, could adoptively transfer delayed-type hypersensitivity reactivity onto naive mice. Taken together, these data suggest that both Th1 and Th2 CD4+ lymphocytes may be activated during experimental C. albicans infection in mice.

Anti-Candida resistance in the mouse brain and effect of intracerebral administration of interleukin 1

The effects of intracerebral and intravenous Candida albicans infection on experimental meningo-encephalitis in mice were compared. Naive mice inoculated with two C. albicans strains of different pathogenicity (highly virulent CA-6 and poorly virulent PCA-2) were more resistant to infection when the yeasts were inoculated by the intracerebral rather than the intravenous route. In immunized mice, in which systemic immunity had been induced by long-term colonization with low-virulence PCA-2 cells, increased intracerebral resistance to challenge with virulent Candida was observed at about two weeks post-infection. In contrast, the inoculation of PCA-2 cells directly into the brain resulted in early, long-lasting activation of local microbicidal mechanisms against intracerebral challenge with CA-6, Staphylococcus aureus or Aspergillus fumigatus. Increased local anti-Candida resistance was also observed upon intracerebral injection of human recombinant interleukin 1. These data suggest that, in addition to the intracerebral expression of systemic antifungal immunity, microbial mechanisms may be locally activated in the brain, possibly through release of endogenous interleukin 1.

Candida albicans-specific Ly-2+ lymphocytes with cytolytic activity

To determine whether antigen (Ag)-specific cytotoxic T lymphocytes are generated during experimental Candida albicans infection, purified L3T4+ and Ly-2+ lymphocytes from immunized mice were cultured in the presence of syngeneic accessory cells, C. albicans Ag, and interleukin 2. Yeast-infected bone marrow macrophages were used as target cells in a standard 51Cr-release assay. Freshly isolated L3T4+ and Ly-2+ lymphocytes failed to lyse either target cell type. However, Ag-specific, major histocompatibility complex (MHC)-unrestricted lysis of infected macrophages was evident with immune Ly-2+ cells after 7-10 days in culture. The cultured cells were greater than 98% Thy-1+, CD3+, L3T4-, Ly-2+, T cell receptor alpha/beta + T cells, and their lytic activity was potentiated by the addition of anti-CD3 monoclonal antibodies. At limiting effector cell numbers, Ag-specific MHC-restricted lymphocytes with cytotoxic activity against infected macrophages could be identified. We suggest that C. albicans infection stimulates multiple cytotoxic cell precursors with varying recognition stringency, which include MHC class I-restricted, Ag-specific cytotoxic T lymphocytes.

Intrasplenic immunization for the induction of humoral and cell-mediated immunity to nitrocellulose-bound antigen

Intrasplenic immunization of mice has been shown to induce both specific humoral and cell-mediated immunity to minute amounts of nitrocellulose-bound antigen, electroblotted from sodium dodecyl sulfate-polyacrylamide gels. The test antigens used were aberrantly expressed molecules immunoprecipitated from the lysate of highly immunogenic ('xenogenized') murine lymphoma cells, derived by mutagenesis from a parental, nonimmunogenic cell line. The stained bands of nitrocellulose blots corresponding to the appropriate molecular weights were cut out and the resulting strips deposited in the spleens of recipient mice on three occasions at 15 day intervals. 2 weeks later, the antibody response in the serum was analyzed using a standard ELISA procedure. Cell-mediated immunity was investigated in vitro in terms of cytotoxic T lymphocyte (CTL) activity to radiolabeled xenogenized tumor target cells. In vivo, the immunized mice were assayed for their ability to mount a delayed-type hypersensitivity (DTH) response following footpad challenge with the xenogenized tumor. Our results confirm previous data that the intrasplenic deposition of minute amounts of protein immobilized on a solid matrix effectively stimulates production of specific antibodies. In addition, our results demonstrate that this procedure may also result in the development of T cell-dependent responses detectable in in vitro and in vivo assays of cell-mediated immunity.