Thymosin alpha1 activates the TLR9/MyD88/IRF7-dependent murine cytomegalovirus sensing for induction of anti-viral responses in vivo

Reactivation of latent human cytomegalovirus following allogeneic transplantation is a major cause of morbidity and mortality and predisposes to severe complications. Thymosin alpha1 (Talpha1), a naturally occurring thymic peptide, is approved for treatment of some viral infections and as an immune adjuvant. Talpha1 successfully primed dendritic cells (DCs) for anti-microbial T helper type 1 resistance through Toll-like receptor (TLR) 9 signaling. We sought to determine here whether Talpha1 could play a role in murine cytomegalovirus infection (MCMV). To this purpose, susceptible, resistant and TLR-deficient mice were infected with MCMV, treated with Talpha1 and assessed for protection in term of microbiological and immunological parameters. Talpha1 protected susceptible and resistant mice from MCMV infection. The anti-viral effect of Talpha1 occurred through the activation of plasmacytoid DCs via the TLR9/myeloid differentiation primary response gene 88-dependent viral recognition sensing, leading to the activation of IFN regulatory factor 7 and the promotion of the IFN-alpha/IFN-gamma-dependent effector pathway.     

Interleukin-1 alpha gene-transcription in murine keratinocytes is inhibited by HSV-1 infection

The effect of in vitro infection with herpes simplex virus 1 (HSV-1) on the Interleukin-1 (IL-1) activity of murine keratinocytes was investigated. IL-1 alpha mRNA synthesis was measured by the Northern blot technique, and the IL-1 protein production was measured in terms of the ability of dialysed supernatants from cultures of uninfected and HSV-1 infected keratinocytes to enhance mitogen-induced murine thymocyte proliferation. IL-1 alpha mRNA-synthesis in uninfected keratinocytes was detected 24 h and 48 h after isolation of the keratinocytes. IL-1 protein secretion by these keratinocytes was measureable at 18 h and reached a peak of 73 h, whereas intracellular and membrane-bound IL-1 protein production reached a maximum after 25 h. Keratinocytes, which had been cultured in vitro for 18 h, were infected with HSV-1 for 2 h and further cultured for an additional 4 h or 22 h before IL-1 measurements. A marked reduction of IL-1 alpha gene-expression was noted 6 hours after HSV-1-infection of keratinocytes, and nearly total shut-off was detected after infection for 24 h. Reduced gene-expression was paralleled by a reduction in the IL-1 protein secretion from the HSV-1 infected keratinocytes.     

Alteration of thymic cell subsets by cocaine administration and murine retrovirus infection in protein undernourished mice.

Retrovirus infection, cocaine administration, and nutritional deficiencies are known to individually produce impairment of the immune system. Therefore, we developed a murine model to study the effect of daily cocaine administration, protein malnutrition, and retrovirus infection causing murine AIDS on the lymphoid cell populations of the thymus. C57BL/6 female mice fed a diet containing 4% protein were studied following chronic cocaine administration and LP-BM5 murine leukemia virus (MuLV) infection. Cocaine administration reduced body and thymus weight. Cocaine partially prevented thymus enlargement due to lymphoid cell proliferation induced by murine retrovirus infection. Cocaine treatment affected dramatically the thymus of protein-malnourished mice where the absolute number of Thy 1.2+, CD4+ and CD8+ cells represented only 10% of the control values. Daily saline injection also induced a significant decrease in the number of Thy 1.2+, CD4+ and CD8+ cells per thymus. These results suggest that the thymus glands of mice fed a low protein diet were susceptible to stress. Retrovirus infection provoked a decrease in the percentage and absolute number of Thy 1.2+, CD4+ and CD8+ cells in the thymus. This effect was potentiated by cocaine treatment. Therefore, cocaine was able to potentiate the impairment of the immune system caused by MuLV infection. We consider that cocaine could alter the immune system by altering the expression of T cell differentiation markers after direct interaction with thymocytes or through the neuroendocrine-thymus axis. Moreover, this effect was more dramatic and severe during protein malnutrition.     

Ex vivo triggering of T-cell-mediated immune responses by autologous tumor cell vaccine in oral cancer patients

We investigated immunomodulatory activity of autologous tumor cell vaccine from oral cancer patients ex vivo by lymphoproliferation assay and two color flow cytometry. Vaccine treatment lead to 10-fold higher proliferation of lymphocytes compared with the untreated controls. A significant increase in CD69(+) and HLA-DR(+) T-cells was observed in vaccine pulsed cultures compared with untreated (p<0.0001) controls. The frequency of IFN-gamma and IL-2 expressing CD4(+)/CD8(+)T-cell subsets was significantly higher with a concomitant reduction in IL-4 and IL-10 expression in the vaccine-treated group (p<0.0001) compared with the untreated controls. Vaccine treatment further increased T-cell receptor Vbeta3, Vbeta5, and Vbeta8 usage. It seems that the autologous tumor cell vaccine triggers T-cell responses ex vivo, hence it may have a protective role in oral cancer patients.     

Modification of spleen cell subsets by chronic cocaine administration and murine retrovirus infection in normal and protein-malnourished mice.

We have developed an experimental mouse model to study the effect of daily cocaine administration on the immune system during an acquired immune deficiency syndrome (AIDS). Mice were infected with LP-BM5 murine leukemia virus, a retrovirus which causes immunosuppression with the development of functional murine AIDS. Increasing doses of cocaine given by daily intraperitoneal injection for 11 weeks reduced body weight. A daily cocaine injection in some mice as well as a saline injection in others showed a decrease in the percentage of Thy 1.2+, CD4+ and CD8+ cells, while both treatments increased the percentage and absolute numbers of B-cells per spleen. Saline and cocaine treatment induced an increase in gamma-IFN and TNF-alpha production by splenocytes. Cocaine treatment favored a decrease in sIL-2R secretion. Saline and cocaine treatment had slightly different effects on the splenocytes of protein-malnourished mice. Cocaine treatment induced an increase in the percentage of CD8+ cells. Saline and cocaine treatments decreased the number of Mac 1+ cells in the spleen. Moreover, saline- and cocaine-treated protein-malnourished mice splenocytes did not present the increase in gamma-IFN production as well-nourished mice splenocytes showed. Retrovirus-infected mice showed a decrease in the percentage of Thy 1.2+ and CD8+ cells and an increase in the percentage and absolute numbers of CD4+, IL-2R+, Mac 1+ and B-cells. Cocaine partially prevented the enlargement of lymphoid organs due to lymphoid cell proliferation induced by murine retrovirus infection, but had little effect on the elevated percentage of CD4+ cells or B-cells or the depressed numbers of CD8+ cells associated with virus infection. However, cocaine did reduce the number of activated IL-2R+ cells and macrophages (Mac 1+) in addition to reducing the total number of cells per spleen in all subsets in retrovirus-infected mice, but not in uninfected controls. Cocaine treatment and retrovirus infection alone or in combination suppressed the release of sIL-2R into supernatant fluid during in vitro culture of splenocytes. These data illustrate that cocaine treatment modulates cell proliferation in retrovirus-infected mice and thus modifies the absolute number of cells in those subsets already altered by retrovirus infection. Retrovirus-infected and retrovirus-infected cocaine-treated protein-malnourished mice showed similar results.     

Modification of thymic cell subsets induced by long-term cocaine administration during a murine retroviral infection producing AIDS.

LP-BM5 murine leukemia virus (MuLV) infection and cocaine administration are known to impair the murine immune system. We have developed a murine model to study the effect of daily cocaine administration and retrovirus infection on the lymphoid cell populations of the thymus. C57BL/6 female mice were studied following chronic cocaine administration for 11 weeks with simultaneous LP-BM5 MuLV infection. Cocaine administration reduced body and thymus weight, significantly reduced the number of CD8+ cells in the thymus, and partially prevented thymus enlargement due to lymphoid cell proliferation induced by LP-BM5 MuLV infection. Retrovirus infection was associated with a decrease in the percentage and absolute number of Thy 1.2+, CD4+, and CD8+ cells in the thymus, an effect potentiated by cocaine administration. Therefore cocaine impairs thymic function by altering the number of cells expressing T cell differentiation markers in MAIDS.     

Effect of in vivo administration of recombinant murine gamma interferon on in vitro lymphoproliferative responses following immunization with Candida albicans.

The effect of in vivo administration of recombinant murine gamma interferon (rMuIFN-gamma) on in vitro proliferation of lymphocytes to Candida antigens and lectins was examined in naive CBA/J mice and in similar mice colonized with Candida albicans by intragastric (i.g.) intubation and/or inoculated intradermally (i.d.) with the fungus. Lymph node lymphocyte and splenic lymphocyte (splenocyte) responses to soluble cytoplasmic substances derived from C. albicans varied with the route of inoculation of the fungus, the sex of the animal, and the presence or absence of rMuIFN-gamma treatment. In the absence of rMuIFN-gamma treatment, lymphoid cells from lymph nodes draining the site of the i.d. lesion responded well to soluble cytoplasmic substances. Colonization of the gut of female mice with C. albicans either had no effect or promoted better lymph node responses when such animals were also challenged i.d., whereas gut colonization of males followed by i.d. challenge appeared to have a suppressive influence on the level of proliferation in response to antigens in vitro. Antigen-specific splenocyte responses could be detected as well, and they were best in animals inoculated i.g.-i.d. or i.d. only. With the exception of lymph node lymphocytes from male mice, treatment of infected animals, regardless of the route of infection, with rMuIFN-gamma frequently resulted in lowered responses to antigens when comparable treatment groups were examined. With respect to mitogen stimulation, infection with C. albicans, especially i.g. or i.g.-i.d., resulted in a population of lymph node lymphocytes with lower-than-normal responses to concanavalin A but higher-than-normal responses to lipopolysaccharide (LPS). Splenocyte responses to mitogens were not altered as dramatically as the responses of lymph node lymphocytes, but splenocytes from female mice had a suppressed response regardless of the route of exposure to C. albicans, and those from mice which were maximally stimulated with C. albicans, i.e., inoculated i.g.-i.d., also had a suppressed response to concanavalin A. Treatment with rMuIFN-gamma either had no effect on the subsequent splenocyte responses or boosted subnormal mitogen responses toward the normal range. Collectively, these data illustrate that exposure to both C. albicans and rMuIFN-gamma influenced the responses to mitogen and C. albicans antigen of lymph node lymphocyte and splenocyte populations, as detected in vitro by lymphoproliferation. Treatment with rMuIFN-gamma often resulted in increased responsiveness to a B cell mitogen, LPS, and decreased responsiveness to a C. albicans antigen.     

Transtracheal administration of interleukin-12 induces neutrophil responses in the murine lung.

Although the roles of interleukin-12 (IL-12) in the immunomodulation of antigen-specific responses are well characterized, the effects of IL-12 on the respiratory tract following mucosal administration are not well defined. Therefore, we investigated changes in the murine lung shortly after intranasal (i.n.) administration of murine IL-12. We showed that IL-12 induced neutrophil influx to the murine lung in both C57BL/6 and BALB/c mice. Histologic examination revealed that intranasal administration of IL-12 with liposomes induced focal neutrophil infiltration into the alveoli and a significant increase in neutrophils in bronchoalveolar lavage fluids when compared with administration of liposomes alone. In vitro chemotaxis assays indicated that the observed pulmonary neutrophil response induced by IL-12 could have been due in part to the direct chemotactic activity of IL-12 for murine neutrophils.     

Thymosin alpha1 is a time and dose-dependent antagonist of dexamethasone-induced apoptosis of murine thymocytes in vitro

It is well established that glucocorticoid hormones induce apoptosis in immature developing thymocytes. Thymocyte apoptosis can be modulated by growth factors, anti-oxidants and adhesion receptors. We have previously demonstrated that thymosin alpha1 (Talpha1) antagonizes dexamethasone-induced apoptosis of CD4+CD8+ thymocytes. In the present study, we further characterize the dose and time dependence of Talpha1's antagonism of dexamethasone-induced thymocyte apoptosis. Talpha1 is effective at concentrations ranging from 2 to 100 microg/10(6) thymocytes. Talpha1 pre-treatment is necessary to achieve its anti-apoptotic activity. Talpha1 provides temporary protection to thymocytes by slowing dexamethasone's apoptotic activity up to 12 h post dexamethasone treatment. Additionally, Talpha1's activity is not sensitive to cycloheximide treatment, suggesting Talpha1's activity is independent of protein synthesis. Finally, Talpha1 is unable to antagonize apoptosis induced by the reactive oxygen species, H2O2, suggesting Talpha1's antagonism of dexamethasone occurs at the early stages of dexamethasone-induced apoptosis, prior to the production of reactive oxygen species. This evidence suggests that Talpha1 may provide a mechanism to transiently extend the life of a thymocyte during thymic selection.     

In vivo activation of murine peritoneal macrophages by intraperitoneal administration of cisplatin

A single intraperitoneal injection of cisplatin (10 mg/kg body weight) in C3H/He mice increases the total number of peritoneal exudate cells (PEC) and macrophages (m phi) within 24 to 48 h. The total number of PEC from untreated mice ranged from 4 to 5 x 10(6) cells/ml containing 2.5 to 3 x 10(6) macrophages, whereas in cisplatin treated mice total number of PEC ranged up to 25 x 10(6) cells/ml. These PEC contained up to 16 x 10(6) m phi. The macrophages obtained from cisplatin injected mice show enhanced cytotoxicity, cytostasis and binding to Dalton's lymphoma cells in vitro. These activated macrophages release into the culture medium factors having cytolytic and cytostatic effect on Dalton's lymphoma cells. The activated macrophages also show enhanced capacity to release superoxide anions, hydrogen peroxide, lysozyme, arginase and interleukin-1.     

Neutrophils as effector cells of T-cell-mediated, acquired immunity in murine listeriosis.

The control of the infections caused by Listeria monocytogenes, considered an example of an intracellular parasite, is thought to involve co-operation between antigen-specific T cells and activated macrophages. Here we investigated the participation of polymorphonuclear leucocytes in the mechanisms of resistance during the immune phase of the antimicrobial response to L. monocytogenes infection. We found that BALB/c mice were unable to express T-cell-mediated (acquired) immunity to this pathogen in the absence of granulocytes. We propose that neutrophils should be included in the concept of cell-mediated immunity and that their antimicrobial role is not exclusively expressed during the early phases of a primary infection.     

In vivo immune responses to Candida albicans modified by treatment with recombinant murine gamma interferon.

The immunologic effects of in vivo administration of recombinant murine gamma interferon (rMuIFN-gamma) were determined in a murine model of candidiasis. Naive mice were given graded doses of rMuIFN-gamma and then challenged intravenously with Candida albicans. Increased morbidity and mortality were noted in four different strains of mice, viz., BALB/c, A/J, Swiss Webster, and CBA/J, providing the mice had not been immunized with C. albicans before challenge. Quantitative culture of selected organs of Swiss Webster and CBA/J mice surviving treatment with rMuIFN-gamma revealed elevated numbers of C. albicans cells, particularly in the kidneys, but also in the liver, lungs, and spleen. The lungs, livers, and spleen of female CBA/J mice were more protected from increased multiplication of the fungus than were those of males of the same species or female Swiss Webster mice. On the basis of these initial findings, the effect of treatment with 5,000 U of rMuIFN-gamma on immune responses in a gastrointestinal model of candidiasis was determined. CBA/J mice that had been colonized with C. albicans as infants were boosted with a cutaneous inoculation of the fungus when 6 to 10 weeks old; development of delayed hypersensitivity (DH), antibodies, and protective responses was assayed at intervals thereafter. Daily treatment with rMuIFN-gamma (beginning 1 day before cutaneous inoculation) suppressed weak immune responses but had little effect on responses which were strong. For example, DH and anti-C. albicans antibody production were suppressed in animals colonized with C. albicans but not boosted by cutaneous inoculation, and DH was suppressed in uncolonized animals that had been inoculated once cutaneously with the fungus as well. There was no rMuIFN-gamma-induced suppressive effect of DH in mice which had been stimulated maximally with C. albicans, i.e., colonized animals that had been boosted cutaneously with the organisms. Collectively, these data indicate that naive mice or mice with minimal levels of anti-C. albicans sensitivity, females somewhat more so than males, were sensitive to suppressive effects of in vivo treatment with rMuIFN-gamma when challenged with C. albicans. In contrast, under conditions similar to those of humans, in whom underlying immunity to C. albicans is usually present, suppression of host responses to C. albicans was not observed in immunized mice in response to treatment with rMuIFN-gamma.     

Hepatic morphologic and biochemical changes induced by subacute cocaine administration in mice.

The initial event and site of cocaine-induced hepatic injury have not been elucidated. In an attempt to identify the minimal effective dose and the site of injury, we have examined the livers of mice exposed to small daily doses of cocaine, using morphological and biochemical methods. All doses of cocaine greater than 5 mg/kg were able to cause significant elevation of serum glutamic pyruvic transaminase. Light microscopy revealed a progression of centrilobular necrosis as the dose increased from 10-30 mg/kg. The initial morphologic changes observed prior to necrosis included aggregation of intermediate filaments and dilation of rough endoplasmic reticulum with loss of ribosomes. Immunohistochemistry, using antibodies to cytokeratins, showed staining of individual hepatocytes in livers from cocaine-treated animals but not in controls. In contrast to earlier reports, we found little, if any, disruption of mitochondria. In vitro, the direct application of cocaine, norcocaine, and N-hydroxynorcocaine on isolated mitochondria had no effect on the ADP:O or respiratory control ratios, at concentrations up to 2.0 mM. Our studies demonstrate that any early cellular alterations in cocaine-induced hepatic injury are manifested in intermediate filaments and endoplasmic reticulum with no evidence of mitochondrial involvement.     

In vivo induction of apoptosis and immune responses in mice by administration of lipopolysaccharide from Porphyromonas gingivalis.

In vivo administration of Porphyromonas gingivalis lipopolysaccharide (Pg-LPS) to mice induced apoptosis before a specific immune response. Apoptosis was associated with the expression of immunoglobulin and Ia on B cells and of CD5 and several markers on T cells. Apoptosis peaked in the spleen and lymph nodes on day 2, and the second peak occurred in the thymus on day 9. Tumor necrosis factor alpha (TNF-alpha) could mediate apoptosis, because the serum TNF-alpha levels were significantly higher than those of controls at 1 day before apoptosis and recombinant murine TNF-alpha induced apoptosis. The apoptosis induced by Pg-LPS was similar to that induced by Escherichia coli LPS in its basic manner, but it was unique in the response of thymus T cells. It was suggested that Pg-LPS could induce apoptosis for the elimination of early nonspecific activated lymphocytes.     

In vivo modulation of the murine immune response to Francisella tularensis LVS by administration of anticytokine antibodies.

The role(s) of gamma interferon (IFN-gamma), tumor necrosis factor alpha (TNF-alpha), and interleukin-4 (IL-4) in establishment and maintenance of protective immunity to Francisella tularensis LVS in mice (C3H/HeN) was examined by selective removal of these cytokines in vivo with neutralizing antibodies. The 50% lethal dose (LD50) for mice infected intradermally with F. tularensis alone was 136,000 CFU; treatment of mice with anti-IFN-gamma or anti-TNF-alpha at the time of infection significantly reduced (P much less than 0.05) the LD50 to 2 and 5 CFU, respectively. Abrogation of protective immunity, however, was effective only when anti-IFN-gamma or anti-TNF-alpha was administered prior to day 3 postinfection. In contrast, the LD50 for mice treated with anti-IL-4 was repeatedly higher (555,000 CFU) than for controls; this difference, however, was not significant (P greater than 0.05). Thus, IL-4 may be detrimental, while IFN-gamma and TNF-alpha were clearly crucial to the establishment of protective immunity to F. tularensis during a primary infection. The importance of IFN-gamma and TNF-alpha during a secondary immune response to F. tularensis was also investigated. Spleen cells from immune mice passively transfer protective immunity to recipient mice in the absence of confounding antibody-mediated immunity. This passive transfer of immunity, however, was abrogated by treatment of recipient mice with anti-IFN-gamma or anti-TNF-alpha at the time of challenge infection. That anticytokines effectively abrogate protective immunity very early in the course of infection with F. tularensis suggests that T-cell-dependent activation of macrophages for microbicidal activity is unlikely. These T-cell-independent events early in the course of infection may suppress bacterial replication until a T-cell-dependent response ultimately clears the bacteria.     

Evidence for alterations in alpha2-adrenergic receptor sensitivity in rats exposed to repeated cocaine administration

It is well established that cocaine stimulates monoamine transmission by blocking reuptake of norepinephrine (NE), dopamine and serotonin into nerve cells, yet few investigations have addressed the effects of chronic cocaine on NE function. In the present study, we examined the effects of repeated cocaine injections on neuroendocrine responses evoked by the alpha2-adrenergic receptor agonist, clonidine. Previous findings show that clonidine increases pituitary growth hormone (GH) secretion by a central mechanism involving postsynaptic alpha2-adrenergic receptors. Male rats previously fitted with indwelling jugular catheters received two daily injections of cocaine (15 mg/kg, i.p.) or saline for 7 days. At 42 h and 8 days after treatment, rats were challenged with clonidine (25 microg/kg, i.v.) or saline, and serial blood samples were withdrawn. Plasma GH and corticosterone levels were measured by radioimmunoassay. Prior cocaine exposure did not affect basal levels of either hormone. However, cocaine-pretreated rats displayed a significant reduction in clonidine-evoked GH secretion at 42 h, and this blunted response was still apparent 8 days later. Corticosterone responses produced by clonidine were similar regardless of pretreatment. The present data suggest that withdrawal from repeated cocaine injections may be accompanied by desensitization of postsynaptic alpha2-adrenoreceptors coupled to GH secretion. Since human patients with depression often exhibit blunted GH responses to clonidine, our findings provide evidence that cocaine withdrawal might produce depressive-like symptoms via dysregulation of NE mechanisms.     

The effects of continuous administration of murine interleukin-1 alpha in the rat

Recombinant murine IL-1 alpha was administered continuously to rats by means of osmotic pumps implanted intraperitoneally. Continuous infusion of rIL-1 alpha in a range between 0.12 and 12.0 micrograms/day for four days was found to produce concentration-dependent weight loss. Behavioral parameters were continuously monitored and recorded at the 3.0 micrograms/day concentration in electronically-monitored activity cages during Days 2 through 5 of rIL-1 alpha administration. Parameters were separated into those affected during the dark phase (active period) or the light phase (resting period). Eating activity was found to be significantly reduced during each dark period through day 5, when compared with either untreated or PBS vehicle-infused animals. During the fourth and fifth days of infusion, however, eating behavior in animals infused with rIL-1 alpha began to increase toward control level in the latter, but not the earlier, half of the dark period. In contrast, drinking behavior was found to be significantly elevated only during the light periods. Continuous infusion of rIL-1 alpha also produced significant reductions in both horizontal locomotor activity (crossovers) and vertical locomotor activity (rears). However, in contrast to the trend toward a return of normal eating behavior, locomotor activity remained decreased through the fifth day of rIL-1 alpha infusion. These results suggest changes that could be produced by IL-1 in chronic inflammatory disease and infection.     

Prothymosin alpha restores the depressed autologous and allogeneic mixed lymphocyte responses in patients with systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is characterized by a variety of profound T-cell abnormalities among which are decreased autologous and allogeneic mixed lymphocyte reactions (auto-MLR and allo-MLR, respectively). In a group of 10 patients with SLE, the mean auto-MLR and allo-MLR responses, tested by tritiated thymidine incorporation, were significantly decreased. If optimal doses of highly purified prothymosin alpha (ProT alpha) were present during the auto- of allo-MLR, the T-cell proliferative responses of SLE patients were increased to normal levels. ProT alpha had more pronounced enhancing effect in patients than in normal individuals. Among patients, ProT alpha was more effective in those who had active disease and low proliferative responses. These results demonstrate that ProT alpha can fully restore the deficient T-cell proliferative responses in auto- and allo-MLR in patients with SLE. ProT alpha, or a certain peptidic fragment of it, could prove potentially useful in the treatment of SLE.     

Regulation of murine in vivo IgG and IgE responses by a monoclonal anti-IL-4 receptor antibody

Although the cytokine interleukin 4 (IL-4) stimulates LPS-activated mouse B lymphocytes to secrete both IgG1 and IgE, an anti-IL-4 antibody completely inhibits IgE responses but has little or no effect on several in vivo IgG responses. IL-4 might, therefore, have a restricted role in the generation of in vivo humoral immune responses. Alternatively, IgG1 responses might be stimulated by IL-4 secreted by T cells that are interacting directly with B cells, so that anti-IL-4 antibody cannot neutralize IL-4 before it binds to a B cell IL-4 receptor. In contrast, an antibody that blocks the IL-4 receptor (IL-4R) should equally inhibit responses to IL-4 produced proximal to or distant from a B cell. This reasoning led us to determine the ability of an anti-IL-4R mAb to affect antibody production in mice injected with a goat antibody to mouse IgD (GaM delta) or inoculated with the nematode parasite Heligmosomoides polygyrus. Anti-IL-4R mAb, like anti-IL-4 mAb, blocked IgE responses by greater than 95% and enhanced IgG2a responses to a variable extent. Anti-IL-4R mAb, however, had only a modest and variable inhibitory effect on the induction of IgG1 responses, although it caused these responses to terminate more rapidly. A combination of anti-IL-4 and anti-IL-4R mAbs totally blocked goat anti-mouse IgD antibody (GaM delta)-induced IgE production but had no additive inhibitory effect on IgG1 production. These observations are most consistent with the view that IL-4 is required for a primary IgE response, but has relatively little role in the induction of IgG1 responses in the in vivo systems studied.