Depressed antibody responses to exogenous antigens in mice with lupus-like graft-versus-host disease

Previous work has established that a disease resembling systemic lupus erythematosus (SLE) can be induced in certain nonirradiated F1 mice undergoing a suitable graft-versus-host reaction (GVHR), e.g., (C57BL/10 X DBA/2)F1 mice injected with DBA/2 T cells. Here, we studied the antibody responses of such autoimmune graft-versus-host F1 mice to exogenous antigens, i.e., sheep erythrocytes, trinitrophenyl keyhole limpet hemocyanin, and levan. We found that primary antibody responses, in particular of IgG isotype, to the T-dependent antigens, sheep erythrocytes, and trinitrophenyl keyhole limpet hemocyanin were strongly suppressed during the entire observation period. Secondary anti-sheep erythrocyte responses, however, were normal, although the peak response was delayed for about 3 days. In contrast to the long-lasting depression of responses to T-dependent antigens, primary antibody responses to the T-independent antigen levan were depressed only at an early stage (i.e., week 2) of the graft-versus-host reaction. In spite of their depressed antibody responses to exogenous antigens, the graft-versus-host F1 mice showed increased numbers of spleen cells spontaneously secreting IgG, and produced IgG autoantibodies characteristic of systemic lupus erythematosus. Mixing experiments performed in vitro with cultures involving graft-versus-host spleen cells revealed that the decreased antibody formation cannot be attributed to suppressor T cells nor to a defect in helper T-cell function. Instead, the mechanism of decreased immune reactivity in SLE-like GVHR seems to operate at the level of B cells. Parallels between the decreased immune reactivity observed in lupus-like GVH disease and that described in human SLE as well as in spontaneously arising murine SLE are discussed.     

The association between lung innate immunity and differential airway antigen- specific immune responses

The mechanisms involved in the differential regulation of airwayimmune responses in atopic versus non-atopic individuals arepoorly understood. In this study, the association between nonspecific immunity and the differential airway antigen-specificImmune responses was examined in a murine model. The disparityIn antigen-specific IgE and IgG2a productions between the twostrains of mice was observed to be significant. C57BL/6J micewere much more efficient than BALB/cJ mice in making IgE antibodyto Inhaled ovalbumin (OVA) antigen. On the contrary, BALB/cJmice did make more IgG2a antibodies than C57BL/6J mice to InhaledOVA. These findings suggest that in C57BL/6J mouse strain apredominant T_h 2 type of Immune response develops in responseto inhaled OVA antigen. In contrast, BALB/c mice mount a T_h1 type of immune response to aerosollzed OVA antigen. Furthermore,after lipopolysaccharlde (LPS) stimulation, the IL-12 mRNA expressionof lung-derived cells from BALB/cJ mice was higher than thatfrom C57BL/6J cells. However, the lung-derived cells of C57BL/6Jmice stimulated by LPS produced higher levels of IL-b and prostaglandinE than BALB/cJ lung-derived cells did. Therefore, our studydemonstrated that the difference of lung-derived cells in theirability to produce cytokine and prostaglandln between BALBIcJand C57BL/6J mice correlates well with the type of the airwayantigen-specific immune effector functions.     

Immunological status of nude mice engrafted with allogeneic or syngeneic thymuses

Restoration of T-cell functions and changes in autoantibody production were studied in BALB/c nu/nu (nude) mice engrafted with syngeneic (BALB/c) or allogeneic (C57BL/6J) thymuses across major histocompatability barriers. T-cell functions, including mitogen responses and antibody production to sheep red blood cells (SRBC), were restored in nude mice engrafted with either allogeneic or syngeneic thymuses. Alloreactivity was evaluated by analysis of the pattern of skin allograft rejection, generation of alloreactive cytotoxic T-lymphocytes (CTLs), or quantitation of mixed-lymphocyte reaction (MLR). BABL/c nude mice engrafted with thymuses from newborn C57BL/6J mice accepted the skin from either thymus donor-type mice or from host-type mice. By contrast, such thymic chimeras rejected skin grafts from a third-party donor. CTLs from nude mice engrafted with C57BL/6J thymuses were cytotoxic to target cells of the third party but not to target cells of the host-type or of the thymus-type. In the MLR assay, spleen cells of nude mice engrafted with C57BL/6J thymuses responded vigorously to third party cells and only slightly to cells of the thymus-type. Low levels of serum IgG and high titers of IgM antibodies to nuclear antigens (but not dsDNA) or skin basal cells were also found in nude mice. Antibodies to both nuclear antigens and skin basal cells disappeared after transplantation of syngeneic thymuses, but not after transplantation of allogeneic thymuses. By contrast, serum IgG levels were restored to normal in nude mice engrafted with either syngeneic or allogeneic thymuses. These results suggest that either HLA-matched or HLA-mismatched thymus grafts may become a viable treatment for certain patients with T cell deficiencies associated with deficient development or maintenance of thymic structure and/or function.     

Correlation between levels of immunoglobulins and immune complexes in plasma of C57BL/6 and C57L/J mice infected with MAIDS retrovirus.

Infection with helper-free, defective MAIDS murine leukemia virus (MuLV) caused a rapid polyclonal activation of B cells in 0.75-, 2-, and 6-month-old C57L/J mice (H-2b, Fv-1n/n), similar to that in C57BL/6 mice (H-2b, Fv-1b/b), which was recognized by elevated plasma immunoglobulin concentrations. However, changes in plasma immunoglobulin levels differed in C57BL/J and C57BL/6 mice. In C57L/J mice, infection resulted in a rapid increase in plasma IgM and IgG2a, and the elevation of IgG2a persisted undiminished for 21 weeks. Levels of IgG2b also became slightly elevated, but those of IgG1 and IgG3 were not significantly affected. Plasma of 6 to 7-month-old C57BL/6 mice contained already high levels of IgM (30-40 mg/ml), which persisted undiminished in uninfected mice but decreased progressively in infected mice to 10% of the original concentration during 25 weeks of observation. In C57BL/6 mice, plasma IgG1 and IgG2b as well as IgG2a became similarly elevated after infection but also only transiently. Their levels began to decrease progressively about 10 weeks after infection and fell to far below the maximum concentration observed. The drastic loss of plasma IgM and IgGs observed in C57BL/6 mice during the later stages of MAIDS MuLV infection did not seem to be a consequence of the polyclonal activation of B cells per se but seemed to reflect additional immunological abnormalities arising in infected C57BL/6 but not C57L/J mice. In both mouse strains these changes in plasma Ig levels correlated with the formation of Ig-containing immune complexes that bound to high-affinity, protein-binding ELISA plates in the absence of antigen coating, which may represent unusual forms of self-antigen-antibody complexes.     

Specificity of helper T cells for different antigens.

BALB/c nude mice have been injected with 10(6) congenic thymus cells, a number which allows some, but not all mice to respond to any particular T-dependent antigen. These mice have been tested for their ability to respond to three bacteriophages, T4, T7 and phiX, sheep and horse erythrocytes, and alloantigens of C3H and C57BL/6 mice. The number of mice able to respond to each of these antigens was of the same order of magnitude. Sheep and horse erythrocytes showed cross-reactivity at the T cell level, i.e. the responses to these two antigens were not independent. The same was observed for C3H and C57BL/6. Otherwise, the responses were independent showing that the antigens are recognize by different populations of specific helper T cells.     

Defective immunoglobulin M responses to vaccination or infection with Schistosoma mansoni in xid mice.

Mice vaccinated with irradiated Schistosoma mansoni cercariae develop a persistent immunoglobulin M (IgM) antischistosomulum antibody response. To investigate the possible role of antilarval IgM antibodies in the effector mechanism of vaccine-induced immunity, CBA/N mice, which have an X-linked genetic defect resulting in impaired IgM antibody responses to certain antigens, were analyzed for their resistance to a challenge infection. When either infected with unattenuated parasites or vaccinated with irradiated cercariae, mice of this inbred strain failed to produce detectable IgM antibodies to schistosomulum surface membrane and soluble worm antigens. To analyze the effect of this IgM deficiency on immunity, F1 hybrids were constructed between CBA/N females and nondefective C57BL/6J males. As expected, vaccinated (CBA/N X C57BL/6J)F1 females, as well as (CBA/J X C57BL/6J)F1 males and females, produced normal IgM antibodies to both surface antigens and worm antigen extracts. However, such antibodies were not produced by (CBA/N X C57BL/6J)F1 males (hemizygous for xid). Nevertheless, (CBA/N + C57BL/6J)F1 males displayed the same high levels of immunity to challenge infection as (CBA/N X C57BL/6J)F1 females and (CBA/J X C57BL/6J)F1 males and females. These results indicate that vaccine-induced immunity is not dependent on an IgM response to schistosome antigens.     

Immune response gene regulation of the humoral immune response to Porphyromonas gingivalis fimbriae in mice.

Among various strains of mice immunized orally with Porphyromonas gingivalis fimbriae and adjuvant GM-53 in liposomes, BALB/c and DBA/2 mice (H-2d) were found to be high responders to the fimbriae, CBA/J and C3H mice (H-2k) were intermediate, while C57BL/6 mice were low responders in terms of serum IgG and salivary IgA responses. Furthermore, humoral immune responses were examined using congeneic mice of B10 background showing different H-2 haplotypes, and it was revealed that B10.D2 mice (H-2d), followed by B10.BR (H-2k), responded well to antigenic stimulation of the fimbriae, while C57BL/10 mice (B10, H-2b) were low responders to the fimbriae. Hybrids between BALB/c and C57BL/6 mice were found to reflect a phenotype of low responders. Thus, the humoral immune responses to P. gingivalis in mice are restricted by H-2 haplotype.     

Secretory antibodies reduce systemic antibody responses against the gastrointestinal commensal flora

The humoral response to the gastrointestinal (GI) flora was analyzed in secretory Ig (sIg)-deficient polymeric IgR (pIgR)(-/-) mice and otherwise congenic C57BL/6 mice. While both strains carried an ileal flora of similar size and composition, increased bacterial translocation to mesenteric lymph node was demonstrated in pIgR(-/-) mice. Serum IgA was greatly increased in pIgR(-/-) mice compared with C57BL/6 mice and reacted with commensal organisms and food. Serum IgG levels in pIgR(-/-) mice were increased to 6-fold above that of C57BL/6 mice and included specificities that bound to selected flora antigens. The enhanced recognition of flora antigens in pIgR(-/-) mice was explored using ovalbumin (OVA)-specific CD4(+) T cells and feeding of low concentrations of OVA. Increased proliferation of transgenic T cells was observed in pIgR(-/-) mice, relative to C57BL/6 mice, suggesting elevated net uptake of protein antigens from the GI tract in the absence of sIg. These studies suggest that there is increased recognition of GI flora antigens by systemic antibodies in pIgR(-/-) mice, most probably as a result of increased access of antigens from the GI flora to the systemic immune compartment, and support the hypothesis that a major function of the secretory immune system is to return environmental antigens to mucosal surfaces.     

Mechanism of Enhanced Humoral Response in Rodents by a Synthetic Polymer

We previously reported that administration of a low molecular weight (MW=800) synthetic polymer, NED 137, significantly increases humoral and cellular immune responses in the rat. The effect of NED 137 on the murine humoral response to T-dependent (TD) and T-independent (TI) antigens was studied in C57 BL/6, CBA/J and Balb/c mice. The TD antigens (SRBC, DNP-DA with adjuvant) or TI antigen (DNP-Ficoll) were administered simultaneously with NED 137. The polymer significantly increased the direct PFC response to all antigens tested in normal mice. However, it could not restore the PFC response to SRBC in athymic (nu/nu) mice. The effect of NED 137 on accessory cells was studied by the assessment of the in vitro response to SRBC in normal and macrophage-depleted rat spleen cultures. The polymer stimulated both, the primary and secondary IgM response and its immunopotentiating activity was the greatest in macrophage-depleted spleen cell preparations. The lack of effect of NED 137 in systems devoid of functional T cells, dependency on and specificity for a sensitizing antigen and its ability to stimulate a secondary response suggest that this polymer does not act as a “conventional” B-cell polyclonal activator.     

Mechanism of Enhanced Humoral Response in Rodents by a Synthetic Polymer

Abstract

We previously reported that administration of a low molecular weight (MW=800) synthetic polymer, NED 137, significantly increases humoral and cellular immune responses in the rat. The effect of NED 137 on the murine humoral response to T-dependent (TD) and T-independent (TI) antigens was studied in C57 BL/6, CBA/J and Balb/c mice. The TD antigens (SRBC, DNP-DA with adjuvant) or TI antigen (DNP-Ficoll) were administered simultaneously with NED 137. The polymer significantly increased the direct PFC response to all antigens tested in normal mice. However, it could not restore the PFC response to SRBC in athymic (nu/nu) mice. The effect of NED 137 on accessory cells was studied by the assessment of the in vitro response to SRBC in normal and macrophage-depleted rat spleen cultures. The polymer stimulated both, the primary and secondary IgM response and its immunopotentiating activity was the greatest in macrophage-depleted spleen cell preparations. The lack of effect of NED 137 in systems devoid of functional T cells, dependency on and specificity for a sensitizing antigen and its ability to stimulate a secondary response suggest that this polymer does not act as a “conventional” B-cell polyclonal activator.     

Immune protection against HSV-2 in B-cell-deficient mice

The role of antibody in protection of the vaginal mucosa and sensory ganglia against HSV-2 infection was examined using HSV- immune, B-cell-deficient muMT mice. Significantly higher virus titers were detected in the vaginal mucosae of immune muMT mice compared to immune C57BL/6J mice 24 h after HSV-2 rechallenge. However, virus was rapidly cleared in immune muMT mice, and the infection was resolved with only a 2-day delay. Passive transfer of immune serum to immune muMT mice prior to rechallenge resulted in HSV-specific vaginal IgG levels comparable to those of immune C57BL/6J mice. Although transferred antibody failed to prevent reinfection of the majority of recipients, vaginal virus titers at 24 h and clearance kinetics were similar to those of immune C57BL/6J controls. Following vaginal rechallenge, HSV-2 did not spread to the sensory ganglia of immune C57BL/6J mice nor was the rechallenge virus detected in the ganglia of the majority of immune muMT mice. However, protection was severely compromised by T-cell depletion of immune C57BL/6J mice. These results suggest that HSV-specific antibody limits, but does not prevent, infection of the genital epithelia. Further, prevention of virus spread to the sensory ganglia in immune animals requires vigorous T-cell immune responses.     

Serum antibody and ocular responses to murine corneal infection caused by Pseudomonas aeruginosa.

The serum antibody response and differential corneal response to primary and secondary infections by Pseudomonas aeruginosa were investigated in DBA/2J (resistant) and C57BL/6J (susceptible) mice, since they respond differently to intracorneal challenge. Using an enzyme-linked immunosorbent assay, we found that naturally resistant DBA/2J mice mounted a significant immunoglobulin M (IgM) and IgG response to P. aeruginosa within 7 days postinfection of one eye; this was subsequently followed by a drop in the IgM response. Of 31 mice, 30 were able to restore corneal clarity within 3 to 4 weeks. However, when C57BL/6J mice were infected intracorneally, their levels of serum antibody developed more slowly than did those of the DBA/2J mice, and they were unable to restore corneal clarity within 8 to 12 weeks. None of the mice from either test strain mounted a detectable serum IgA response to P. aeruginosa over a 90-day holding period. However, infection of the contralateral, normal cornea of mice of both test strains resulted in a heightened IgG response to P. aeruginosa within 30 days after the secondary infection. Many (50%) of the susceptible C57BL/6J mice recovered or exhibited less severe corneal damage within the 30-day holding period. If the C57BL/6J mice were reinfected 60 days after the primary infection instead of after 30 days, most (89%) of the mice had restored corneal clarity within 3 to 6 days. Passive transfer of immune serum from either recovered DBA/2J or C57BL/6J mice to naive C57BL/6J mice resulted in the restoration of corneal clarity in many of the recipients following infection.     

Limited T Helper Cell Activity in C57BL/10 (B10) Mice with Inherited Low IgG Responsiveness

Due to limitations in antigen processing, mice of the C57BL/10ScSn (B10) strain exhibit a low IgG production against a variety of T-dependent antigens. To characterize the T-cell functions, the authors studied antigen-specific T-cell proliferation and cytokine production in vitro . The response of B10 mice was compared with that of the high IgG producing strain A/J. A highly restricted proliferative response and almost no interleukin-2 (IL-2) and interleukin-3 (IL-3) production was detected in lymph node (LN) cells of B10 mice primed in vivo by protein antigens and subjected to a specific restimulation in vitro , whilst A/J cells responded by significant proliferation and cytokine production. The antigen-specific T-cell response of B10 mice could not be increased by lipopolysaccharide treatment in vivo or by in vitro cultivation with IL-2. However, the T cells of B10 mice produced high levels of IL-2 and IL-4 when stimulated by phorbol myristate acetate (PMA) and Ca²⁺ ionophore, proving the existence of a functionally intact signal transduction pathway downstream of protein kinase C (PKC). The results suggest that the in vivo antigen priming does not effectively activate the T cells in B10 mice. The limited activation consequently leads to the low IgG response described in B10 mice.     

IgG response is impaired in H2-c-fos transgenic mice.

Transgenic mice carrying the proto-oncogene c-fos under the control of H-2Kb promoter (c-fos mice) were generated from (C57BL/6 x SJL)F2 mice. One line was backcrossed with C57BL/6 mice for 10 generations. These semi-congenic c-fos mice express exogenous c-fos RNA in their hematopoietic tissues. The following immunological states are apparent. (i) Titers of serum IgM, IgG, and IgA of naive c-fos were within the control range. (ii) These mice could not produce primary IgG antibody specific for immunized antigen. (iii) Production of primary IgM and IgA antibody to the antigen was within the control range. (iv) There were no IgG memory B cells generated in the spleens of c-fos mice. (v) Activities of antigen-presenting cells and carrier-specific helper T cells from c-fos mice were normal. These findings strongly suggest that the immune abnormality of c-fos mice is in limiting B cell function to the production of IgG to immunized antigens.     

Antibody-mediated protection against Cryptococcus neoformans pulmonary infection is dependent on B cells

The pathogenesis of pulmonary Cryptococcus neoformans infection and the efficacy of passive immunoglobulin G1 (IgG1) administration were investigated in B-cell-deficient and C57BL/6J mice. C57BL/6J mice lived longer than B-cell-deficient mice after both intratracheal and intravenous infections. Administration of IgG1 prior to infection prolonged the survival of C57BL/6J mice but had no effect on the survival or numbers of CFU in the lungs of B-cell-deficient mice. C. neoformans infection in B-cell-deficient mice resulted in significantly higher levels of gamma interferon (IFN-gamma), monocyte chemoattractant protein-1 (MCP-1), and macrophage inflammatory protein-1alpha (MIP-1alpha) than in C57BL/6J mice. IgG1 administration reduced IFN-gamma and MCP-1 levels in C57BL/6J mice but not in B-cell-deficient mice. In addition, compared to its effect in C57BL/6J mice, C. neoformans infection in FcRgammaIII-deficient, athymic, and SCID mice significantly increased IFN-gamma and MCP-1 levels. IgG1 administration was associated with reduced IFN-gamma levels in C57BL/6J mice but not in FcRgammaIII-deficient, athymic, and SCID mice. These observations suggest that IgG1-mediated protection in this system is a consequence of alterations in the inflammatory response that translate into less damage to the host without directly reducing the fungal burden. For hosts with impaired immunities, the ineffectiveness of passive antibody (Ab) may reflect an inability to down-regulate inflammation and avoid self-damage. The results indicate an important role for B cells in host defense against C. neoformans infection and demonstrate a surprising dependence of Ab-mediated protection on B cells in this system.     

Murine cytomegalovirus

BALB/c and C57BL/6 mice were infected with murine cytomegalovirus (MCMV). On day 4 or 12 of the infection, the animals were immunized with SRBC (T-dependent), TNP-Ficoll (T-independent) and standard poliovirus. The adverse effect of the virus infection on humoral immune responses was limited to animals immunized on day 4; while anti-SRBC antibody formation was severely depressed in both mouse strains, reduced plaque forming cells to TNP-Ficoll were registered only in BALB/c mice. Antibodies to poliovirus were depressed in both strains, although to a lesser degree in C57Bl/6 than in BALB/c mice. Anti-SRBC B cell memory was found to be affected by MCMV infection. These results are interpreted to mean that T-dependent and -independent antigens may be handled differently by the two mouse strains tested.     

Candidate vaccine antigens identified by antibodies from mice vaccinated with 15- or 50-kilorad-irradiated cercariae of Schistosoma mansoni.

In murine schistosomiasis, the highest levels of resistance to cercarial challenge are obtained by vaccination with radiation-attenuated cercariae. To identify candidate vaccine antigens relevant to the vaccine model, we examined parasite antigens recognized by antibodies from mice vaccinated with irradiated cercariae of Schistosoma mansoni. To optimize recognition of a wide spectrum of antigens, several factors that influence the level of protection in this model were varied; specifically, we examined the effect of (i) single versus multiple vaccinations with irradiated cercariae, (ii) the dose of irradiation (15 or 50 kilorads) administered to the cercariae, and (iii) the genetic background of mouse strains, high-responder (C57BL/6J) versus moderate-responder (CBA/J) mice. We found that the number of vaccinations did not alter antibody specificity but modified the relative antibody titers against particular antigens. The dose of irradiation used to attenuate the immunizing cercariae had a similar effect on antibody titers but in addition influenced antibody specificity. Only mice that had been vaccinated with moderately irradiated cercariae recognized cathepsin B (Sm31) and Sm32. Interestingly, when vaccinated mice of the two strains, C57BL/6J and CBA/J, were compared, differences in antibody responses to particular antigens were observed. Both strains recognized the integral membrane protein Sm23, glutathione S-transferase, and cathepsin B, whereas Sm32 and paramyosin were recognized only by CBA/J mice, and heat shock protein 70 was recognized exclusively by C57BL/6J mice. In this study, we conclusively identified six distinct antigens that are specifically recognized by the humoral immune response of vaccinated mice.     

A potential weak allelic difference in male-specific antigen between two inbred strains of mice

Differences were detected between male-specific antigen(s) from BALB/c and C57BL/10 mice. Reciprocal crosses between these strains were analysed by means of a popliteal lymph node assay enumerating cells secreting IgM and IgG in a T-dependent bystander B-cell response. The responses, while being indirect, weak and variable, suggested that there are differences in 'immunogenicity' coded by Y-linked (male-specific) genes. This conclusion was strengthened by the results of experiments carried out in Y-backcross mice, where spleen cells from male C57BL mice with a BALB/c-Y (B10.C-YC) stimulated low popliteal lymph node responses in female littermates in comparison with C57BL mice with their own Y-chromosome. In contradistinction, male spleen cells from a BALB/c with a C57B1/10-Y chromosome (C.B10-YB), injected into a hind footpad of a female littermate, induced a relatively higher popliteal lymph node response.     

Major histocompatibility complex restriction of maternally induced suppression in young adult mice.

This study focused on the mode in which maternal T cells induce suppression of plaque-forming cell (PFC) response in offspring. The maternal T cells of C57BL/6J pregnant mice, which had been intraperitoneally injected with 2 x 10(8) of sheep red blood cells (SRBC) on day 12 of gestation, were transferred, 5 days after immunization, into (C3H/HeJ x C57BL/6J)F1 normal pregnant mice on day 12 of gestation. The (C3H/HeJ x C57BL/6J)F1 x C3H/HeJ offspring of (C3H/HeJ x C57BL/6J)F1 recipient pregnant mice were reared to more than 6 weeks of age, and their anti-SRBC PFC responses were examined. Suppression of anti-SRBC PFC response was observed in H-2bxk but not H-2k offspring. Thus, maternal T cells of SRBC-immunized pregnant mice induce suppression of anti-SRBC PFC in offspring with restriction to major histocompatibility complex (MHC) haplotype utilized in maternal T-cell responses during pregnancy. Maternal CD4+ T cells are responsible for the MHC-restricted induction of PFC suppression in offspring. Furthermore we demonstrated, in this report, using adoptive transfer of maternal T cells from SRBC-immunized pregnant mice and in vitro secondary PFC assay in the offspring, that maternal T-cell-mediated suppression results from the development of CD4+ suppressor T cells in offspring. Moreover, the activation of suppressor T cells in offspring depends on the recognition of SRBC antigens presented in association with the same MHC haplotype as that utilized in the maternal T-cell response during pregnancy. Thus, the maternal T cells of SRBC-immunized pregnant mice generate a repertoire of suppressor T cells in their offspring.     

C57BL/6 mice are more susceptible to antigen-induced pulmonary eosinophilia than BALB/c mice, irrespective of systemic T helper 1/T helper 2 responses

Inflammatory response differences between C57BL/6 and BALB/c mice following ovalbumin (OVA) sensitization and a single challenge were investigated. Serum immunoglobulin (Ig)E and IgG1 levels were higher in C57BL/6 mice than in BALB/c mice. In contrast, IgG2a levels in C57BL/6 mice were lower than in BALB/c mice. Furthermore, the number of eosinophils infiltrating into lungs in C57BL/6 mice was significantly higher than in BALB/c mice after OVA challenge. The levels of the T helper 2 (Th2)-type cytokines interleukin (IL)-4 and IL-5, generated in challenged C57BL/6 lung tissue, were also higher than in BALB/c lung tissue. The participation of IL-4 and IL-5 in the induction of eosinophil infiltration into the lungs was confirmed in both strains of mice by injection of anti-IL-4 and anti-IL-5 monoclonal antibodies (mAbs). However, following OVA stimulation, in vitro IL-4 and IL-5 production in splenocyte cultures from C57BL/6 mice was lower than in splenocyte cultures from BALB/c mice. These results indicate that C57BL/6 mice induce Th2-type responses in the lungs, while BALB/c mice induce T helper 1 (Th1)-type responses in the lungs, despite considerable production of IL-4 and IL-5 from splenocytes. Therefore, local immune responses are more important in the induction of allergic inflammation in the lungs and are different from systemic immune responses, which are thought to depend on genetic background.