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PubMed1977

Immune response of the mammary gland and role of immunization in mastitis control.

It has been mentioned that IgG1 is the major secretory immunoglobulin class in mammary gland secretions; in addition, most immunoglobulins of all classes in these secretions are of humoral origin. A transport mechanism selectively favors IgG1. A lesser amount of immunoglobulin is produced locally in the gland, this local contribution apparently increasing after antigenic stimulation. Therefore, systemic and local stimulation would be likely to contribute to the presence of specific antibodies in secretions. The role of cellular immune phenomena as it relates to the mammary gland has not been determined. There is evidence for the influence of phagocytic cells in the mammary gland. Published reports have established that a state of heightened resistance to mammary gland infection can be induced. Research workers have clearly shown that immunized animals resist challenge exposure to infection to a greater degree than do nonimmunized animals. This resistance, being not absolute, causes reluctance to use the term immune. It is apparent that reexamination must be made of the correct conditions, i.e., effective antigenic preparation, proper inoculation route, dose, and duration necessary to stimulate an immune response in the mammary gland.

Animals↗
PubMed1998

Splenectomy for HIV-related immune thrombocytopenia: comparison with results of splenectomy for non-HIV immune thrombocytopenic purpura.

OBJECTIVE: To determine the effectiveness and safety of splenectomy for patients with human immunodeficiency virus (HIV)-related immune thrombocytopenia, using the results of splenectomy for patients with non-HIV immune thrombocytopenic purpura as a control group for comparison. DESIGN: Retrospective study. SETTING: Tertiary care university hospital. PATIENTS: Fourteen patients who underwent splenectomy for symptomatic, medically refractory HIV-related immune thrombocytopenia at this hospital from 1988 to 1997. During the same period, 20 patients had splenectomy for treatment of non-HIV immune thrombocytopenic purpura. INTERVENTION: Splenectomy. MAIN OUTCOME MEASURES: Platelet response, need for postsplenectomy medical therapy, progression of HIV disease, and complications. RESULTS: All patients with HIV-related thrombocytopenia had a complete early platelet response to splenectomy, with an elevation of the platelet count to greater than 100X10(9)/L. After a median follow-up of 26.5 months, all but 1 patient had a sustained complete remission with no need for medical therapy for thrombocytopenia. Splenectomy was more effective in the HIV-related thrombocytopenia group than in the non-HIV immune thrombocytopenic purpura group, with significantly higher platelet counts at 1 week and 1 month after splenectomy in the HIV group (t test, P=.02 and P=.009, respectively). There were significantly fewer patients needing medical therapy for thrombocytopenia after splenectomy in the HIV group (chi2 test, P=.02). There were no remarkable short- or long-term complications in the patients with HIV infection, including no overwhelming postsplenectomy infections. Three patients have died, and 2 patients have developed AIDS since operation. CONCLUSIONS: Splenectomy is effective treatment for patients with symptomatic HIV-related thrombocytopenia that is resistant to medical therapy. The effectiveness of this treatment suggests that the predominant mechanism of thrombocytopenia in HIV-infected patients is increased destruction of platelets because of platelet-associated immunoproteins.

Adolescent↗
PubMed1998

Rapid formation of the immune complexes on solid phase in the immune complex transfer enzyme immunoassays for HIV-1 p24 antigen and antibody IgGs to HIV-1.

In order to perform the immune complex transfer enzyme immunoassays for HIV-1 p24 antigen and antibody IgGs to HIV-1 p17, reverse transcriptase and gp41 antigens as rapidly as possible, methods for rapid formation of the immune complexes on solid phase are described. HIV-1 p24 antigen was reacted with monoclonal anti-p24 Fab'-beta-D-galactosidase conjugate at a high concentration and subsequently with polystyrene beads coated successively with affinity-purified (anti-2,4-dinitrophenyl group) IgG and 2,4-dinitrophenyl-biotinyl bovine serum albumin-affinity-purified anti-p24 Fab' conjugate. Antibody IgGs to HIV-1 were reacted with polystyrene beads coated successively with affinity-purified (anti-2,4-dinitrophenyl group) IgG and 2,4-dinitrophenyl-HIV-1 antigen conjugates and subsequently with HIV-1 antigen-beta-D-galactosidase conjugates. The periods of time used for the formation of the immune complexes comprising the three components on the polystyrene beads (15-30 min) were much shorter than those used in the previous immune complex transfer enzyme immunoassays (90-300 min), and the sensitivities of the present and previous immune complex transfer enzyme immunoassays were similar. The detection limit of the HIV-1 p24 antigen by the present and previous methods were similar (3 to 10 zmol/assay).

Adult↗
PubMed2001

Immunization with a tumor-associated CTL epitope plus a tumor-related or unrelated Th1 helper peptide elicits protective CTL immunity.

Immunization with cytotoxic T cell epitope SPSYVYHQF (AH1), derived from MuLV gp70 envelope protein expressed by CT26 tumor cells, does not protect BALB/c mice against challenge with CT26 tumor cells. By contrast, immunization with AH1 plus T helper peptides OVA(323-337) or SWM(106-118) eliciting Th1 and Th0 profiles, protected 83% and 33% of mice, respectively. Interestingly, immunization with AH1 plus both helper peptides reverted the efficacy to 33%. We identified the endogenous T helper peptide p(320-333) from gp70 which elicits a Th1 profile and is naturally processed. As for OVA(323-337), immunization with p(320-333) alone did not protect against tumor challenge. However, p(320-333) plus AH1 protected 89% of mice at day 10 after vaccination. Only 20% of mice vaccinated with AH1 + OVA(323-337) or AH1 + p(320-333) were protected when challenged 80 days after immunization. Treatment with OVA(323-337) or with p(320-333) around established tumors delayed tumor growth. Our results show that tumor-related as well as tumor-unrelated but strong Th1 peptides may be useful for inducing CTL responses in tumor immunotherapy.

Adjuvants, Immunologic↗
PubMed1992

Relationship between immune response to melanoma vaccine immunization and clinical outcome in stage II malignant melanoma.

The authors investigated whether there was a relationship between the induction of a delayed-type hypersensitivity (DTH) response to melanoma vaccine immunization and disease recurrence. They studied prospectively 94 evaluable patients with surgically resected Stage II malignant melanoma who were immunized to a partially purified, polyvalent, melanoma antigen vaccine. The DTH response to skin tests to the vaccine was measured before treatment and at the fourth vaccine immunization. Vaccine treatment induced a strong DTH response in 29 (31%) patients, an intermediate response in 24 (25%), and no response in 41 (44%). The median disease-free survival (DFS) of patients with a strong, intermediate, and no DTH response to vaccine immunization was more than 72 months, 24 months, and 15 months, respectively. The relationship between an increase in the DTH response and a prolonged DFS was statistically significant (P = 0.02); clinically meaningful (the median DFS of patients with a strong DTH response was 4.7 years longer than that of nonresponders); and, by multivariate analysis, independent of disease severity or overall immune competence. These findings suggest, but do not prove, that vaccine treatment can slow the progression of melanoma in some patients.

Adult↗
PubMed1988

HIV-specific T lymphocyte immunity in mice immunized with a recombinant vaccinia virus.

Infection by the human immunodeficiency virus (HIV) induces T cell immunity in humans, chimpanzees and macaques. The protective value of this immune response is not clear. We have consequently developed a murine experimental system to study HIV-specific CD4 and CD8 T lymphocyte immunity in vitro and in vivo. BALB/c, DBA/2 and C3H/He mice were immunized with vaccinia virus (VV) recombinant VV-11.39 which expresses the gp160 glycoprotein of HIV-1. Primary and secondary cytotoxic T lymphocyte response to HIV were detected with histocompatible mouse target cells transfected with the HIV-1 env gene. Killer cells were positive for the Thy-1 and Ly-2 (CD8) T cell markers, and were restricted by class I H-2 histocompatibility antigens. Immunological memory specific for HIV-1 envelope antigens was clearly induced by vaccination with VV-11.39:spleen cells from mice vaccinated 4 weeks or more prior to assay generated CD4 and CD8 T lymphocyte responses following stimulation in vitro with HIV envelope antigens. The intensity of these responses increased with consecutive vaccinations, indicating that HIV-specific precursor T cell pools were progressively amplified. Finally, DBA/2 mice vaccinated with VV-11.39 developed protective immunity against a syngeneic tumor which expresses HIV-1 env antigens, leading to accelerated tumor rejection and increased survival.

Animals↗
PubMed1989

Mechanism of immune complex-mediated damage: induction of interleukin 1 by immune complexes and synergy with interferon-gamma and tumor necrosis factor-alpha.

The ability of immune complexes derived from patients with type II mixed essential cryoglobulinemia to trigger the production of interleukin 1 (IL 1) was investigated. Immune complexes containing either IgM/IgG or IgA/IgG aggregates were shown to induce IL 1 production in human peripheral blood monocyte-enriched populations. Interferon-gamma alone did not induce detectable IL 1, but increased the IL 1 production induced by the immune complexes. Tumor necrosis factor-alpha, which is a potent inducer of IL 1, also enhanced IL 1 production following stimulation with suboptimal doses of the immune complex. The findings suggest that immune complexes may induce inflammation partly due to their capacity to induce the synthesis of IL 1.

Antigen-Antibody Complex↗
PubMed1992

Fluids from immune privileged sites endow macrophages with the capacity to induce antigen-specific immune deviation via a mechanism involving transforming growth factor-beta.

The eye, brain, and fetoplacental unit within the pregnant uterus are immunologically privileged sites that contain unique fluids with suspected immunoinhibitory properties. Aqueous humor, which is normally present within the anterior chamber (AC) of the eye, has been shown to suppress antigen-driven T cell activation, and to contain significant amounts of transforming growth factor beta-2 (TGF-beta). Antigens injected into the AC of normal mice induce a deviant form of systemic immunity, termed anterior chamber-associated immune deviation (ACAID), which is characterized by a selective inability to display antigen-specific delayed hypersensitivity. It has recently been reported that eye-derived macrophages appear in the blood following AC injection of a soluble antigen, and that these cells can induce antigen-specific ACAID when injected into naive, syngeneic recipients. Moreover, antigen-pulsed peritoneally derived macrophages that are exposed in vitro to aqueous humor, supernatants of cultured iris and ciliary body cells (I/CD), or TGF-beta have been found to assume ACAID-inducing properties. In the present experiments, amniotic fluid and cerebrospinal fluid from mice, rats and humans, as well as supernatants from cultured I/CB cells, have been examined for their capacity to confer ACAID-inducing properties on peritoneal macrophages. It was found that each of these biologic fluids, but neither normal mouse serum nor rat thoracic duct lymph, was able to endow antigen-pulsed peritoneal macrophages with ACAID-inducing properties. Moreover, fluids from these immune privileged sites were found to contain latent and/or active TGF-beta, as determined by bioassay, using neutralizing anti-TGF-beta antibodies. It is concluded (a) that the immune privileged states of the eye, the brain, and the fetoplacental unit share common features, and possess unique fluids with a similar capacity to force macrophages to present antigens in a "deviant" manner and (b) that this capacity is mediated, at least in part, by TGF-beta. These results are discussed in terms of the potential physiologic and pathophysiologic significance of immune privilege in these three specialized tissues.

Amniotic Fluid↗
PubMed1995

Dendritic cells in Leishmania major-immune mice harbor persistent parasites and mediate an antigen-specific T cell immune response.

Upon infection with Leishmania major, a cause of human cutaneous leishmaniasis, mice of resistant strains are able to control the infection, with lesions resolving spontaneously. A long-lasting cell-mediated immunity protects them from reinfection. Nevertheless, small numbers of viable parasites persist in the lymph nodes of these mice. We have recently documented that, in addition to macrophages, epidermal Langerhans cells can ingest L. major. Furthermore, Langerhans cells have the unique ability to transport viable parasites from the infected skin to the draining lymph node for presentation to antigen-specific T cells and initiation of the cellular immune response. During migration, Langerhans cells develop into dendritic cells. In the present study, we analyzed whether dendritic cells support the persistence of parasites in immune hosts. Immunohistological studies and assays in vitro showed that in the lymph nodes of mice that have recovered from infection with L. major, both macrophages and dendritic cells harbor viable parasites. However, only dendritic cells were able to induce a vigorous T-cell immune response to L. major in vitro in the absence of exogenous antigen. Tracking experiments conducted in vivo suggested that the infected dendritic cells in the lymph nodes are derived from Langerhans cells that have emigrated from the skin. The data demonstrate that L. major-infected dendritic cells and macrophages in lymph nodes of immune animals represent long-term host cells, but only dendritic cells have the ability to present endogenous parasite antigen to T cells. Long-term infected dendritic cells may thus allow the sustained stimulation of a population of parasite-specific T cells, protecting the mice from reinfection. Our results favor the hypothesis that the persistence of antigen supports the maintenance of T cell memory and that dendritic cells are critically involved in this process.

Animals↗
PubMed2003

Generation of an effective anti-tumor immunity after immunization with xenogeneic antigens.

Central and peripheral tolerance mechanisms are expected to hamper the generation of effective immunity against tumors. To break self tolerance against malignant gliomas, we assessed the therapeutic potential of self/foreign antigen cross-reactivity in an immunocompetent rat glioma model. Immunotherapy of tumors using xenogeneic human glioma membrane proteins (HGP) as a vaccine inhibited tumor growth, whereas no significant effect was obtained with rat glioma membrane proteins (RGP). In contrast to RGP, HGP elicited a specific IgG immune response that cross-reacted with RGP. This immune response was found to be mainly a Th1 type response. On tumor sections stained with hematoxylin and eosin, glioma cells are sparse and apoptotic in HGP-immunized rats, whereas control tumors showed condensed and viable cells. Tumor-specific CTL were induced in HGP-immunized rats. Immunohistochemical analysis revealed that a significant number of CD8(+) and CD4(+) cells infiltrated into tumors from HGP-vaccinated rats, whereas RGP vaccination led to only few tumor-infiltrating T cells. Taken together, the data establish the in vivo applicability of the cross-stimulation between self and foreign antigens as an alternative way to break tolerance against the poorly immunogenic gliomas.

Animals↗
PubMed2005

The mouse chorionic gonadotropin beta-subunit-like (muCG beta l) molecule produced by tumor cells elicits the switch of T-cell immunity response from TH2 to TH1 in mice immunized with DNA vaccine based on rhesus monkey homologous CG beta (rmCG beta).

BACKGROUND: CG beta is expressed not only in placenta, but also in a wide range of tumors. To study DNA vaccine based on xenogeneic CG beta for cancer immuno-therapy, we investigated whether rhesus monkey CG beta (rmCG beta) DNA vaccine could induce protective T-cell responses and humoral responses in mouse. METHODS: We constructed a plasmid containing the rmCG beta coding sequence. Two cloned syngeneic SP2/0 myeloma cell lines that stably express muCG beta l (SP2/0-muCG beta l) and HN (SP2/0-HN) protein were established. Inoculation of these cell lines was made into mice that had been immunized with DNA vaccine. Specific IgG and IgG type were measured by ELISA and the cytokine expression was detected with RT-PCR. To measure the lymphocyte metabolic activity, the MTS assay was used. RESULTS: After injection of SP2/0-muCG beta l into mice that had been immunized with DNA vaccine, a significant increase in the IgG2a specific to the antigen (p < 0.05) and a decrease in the specific IgG1 (p < 0.05) were measured. The expression of T(H)1 but not T(H)2 cytokines, including IFN-gamma and IL-2, were detected in the splenocytes. However, injection of tumor cells expressing irrelevant or mock molecules into immunized mice could not induce these changes. The survival rate of vaccine-immunized mice injected with SP2/0-muCG beta l was as high as 58.3% after 55 days. CONCLUSIONS: The rmCG beta DNA vaccine has proved to be a potential strategy for protection against tumors with homologous molecules. The muCG beta l produced by tumors is able to elicit an immunity switch from T(H)2 to T(H)1 in vaccinated mice.

Animals↗
PubMed1987

Immunopathological studies on thyroid immunity. IX. Thyroid and renal amyloidosis in thyroglobulin immunized rabbits.

In serial studies of immunopathologic changes in an animal model of thyroiditis 52 rabbits were immunized with either bovine, porcine or human thyroglobulin (Tg) in Freund's complete adjuvant, while another 47 animals served as noninjected or adjuvant injected controls. The immunized animals were divided into two groups, one receiving an initial series of only three Tg injections while the other received, in addition, challenging injections over an 8-week period. The immunized animals were killed over a period of 6-34 months after the last Tg injection, and untreated controls were killed at comparable ages. In Tg immunized animals, lymphocytic thyroiditis was encountered in 25 per cent and thyroid amyloid in 17 per cent; glomerular amyloid was encountered in 44 per cent with diffuse lesions in 8 per cent, nodular lesions in 17 per cent and a mixture of the two in 19 per cent. That the thyroid and glomerular hyaline deposits contained amyloid was shown by various histochemical criteria, as well as by the presence of typical fibrils on electron microscopy. Immunohistochemical studies indicated that the amyloid was predominantly of the AA type. Rabbits receiving challenging Tg injections, in addition to the initial series, showed only thyroiditis and nodular glomerular lesions most of which were amyloid. Whilst the vast majority of rabbits with lymphocytic or amyloidotic responses showed both thyroid and renal lesions, a small percentage of animals showed only a lesion of one or the other of these two organs. It is of interest that the thyroid and renal amyloid lesions, described for the first time with induced thyroglobulin immunity, were not detected in other earlier short term investigations.

Amyloidosis↗
PubMed1994

Brain monoaminergic, neuroendocrine, and immune responses to an immune challenge in relation to brain and behavioral lateralization.

Host responses to immune challenges involve central neurotransmission, the hypothalamo-pituitary adrenal axis, and the immune system. In the present work, we investigated the possibility of an asymmetry in the modification of brain monoamine metabolism induced by a systemic injection of lipopolysaccharide (LPS) in adult female mice. We also studied the possible influence of behavioral lateralization, as assessed by a paw preference test, on the reactivity of the nervous, neuroendocrine, and immune systems to a LPS challenge. The results showed that LPS administration induced an enhanced brain activity as demonstrated by an increase in noradrenergic, serotoninergic, and dopaminergic metabolism. Increased serotonin metabolism, observed in the hypothalamus and hippocampus, only occurred on the left side. Furthermore, the increase in serotonin turnover in the medial hypothalamus, the elevation of plasma adrenocorticotropin levels, and the decrease in T lymphocyte proliferation were observed in right-handed and ambidextrous mice but not in left-handed animals. Taken together, the results demonstrate that an immune challenge could induce neurochemical, neuroendocrine, and immune responses similar to those of stress, suggesting that LPS may be a stress inducer. Interestingly, these responses that may be asymmetrically expressed appear to depend on behavioral lateralization.

Adrenocorticotropic Hormone↗
PubMed2000

Anti-tumor immunity against CT26 colon tumor in mice immunized with plasmid DNA encoding beta-galactosidase fused to an envelope protein of endogenous retrovirus.

Endogenous retroviral gene products have been recognized as being expressed in human cancerous tissues. However, these products have not been shown to be antigenic targets for T-cells, possibly due to immune tolerance. Since carcinogen-induced colon tumor CT26 expresses an envelope protein, gp70, of an endogenous ecotropic murine leukemia virus that is comparable to human tumor-associated antigens, we examined whether a DNA vaccine containing the gp70 gene induces protective immunity against CT26 cells. Injection of mice with plasmid DNA (pDNA) encoding gp70 alone failed to induce anti-gp70 antibody (Ab) or anti-CT26 cytotoxic T lymphocyte (CTL) responses. However, immunization with pDNA encoding the beta-galactosidase (beta-gal)/gp70 fusion protein induced anti-gp70 Ab and anti-CT26 CTL responses and conferred protective immunity against CT26 cells. These results indicate that beta-gal acts as an immunogenic carrier protein that helps in the induction of immune responses against the poorly immunogenic gp70. Considering these results, it is possible that potential tolerance to the endogenous retroviral gene products expressed by human tumors may be overcome by DNA vaccines that contain an endogenous retroviral gene fused to genes encoding immunogenic carrier proteins.

Animals↗
PubMed1999

Comparison of simian virus 40 large T antigen recombinant protein and DNA immunization in the induction of protective immunity from experimental pulmonary metastasis.

In this report we examine the ability of a recombinant tumor antigen preparation to prevent the establishment of experimental pulmonary metastasis. Baculovirus-derived recombinant simian virus 40 (SV40) large tumor antigen (T-Ag) was injected into BALB/c mice followed by challenge with an intravenous injection of syngeneic SV40-transformed tumorigenic cells. The experimental murine pulmonary metastasis model allows for the accurate measurement of metastatic lessions in the lungs at various times after the challenge, using computer-assisted video image analysis. Following challenge, lung metastasis and survival data for the groups of mice were obtained. Animals immunized with recombinant SV40 T-Ag showed no detectable sign of lung metastasis and survived for more than 120 days after challenge. Antibodies specific for SV40 T-Ag were detected in the serum of immunized mice by enzyme-linked immunosorbent assay. Splenocytes obtained from mice immunized with recombinant SV40 T-Ag did not lyse syngeneic tumor cells, indicating that no cytotoxic T lymphocyte response was induced. Control mice developed extensive lung metastasis and succumbed to lethal tumor within 4 weeks after challenge. These data indicate that immunization with the recombinant SV40 T-Ag induces protective, T-Ag-specific immunity in an experimental pulmonary tumor metastasis model.

Animals↗
PubMed1985

Immune deposits in normal skin of patients with systemic lupus erythematosus: relationship to the serum capacity to solubilize immune complexes.

Immunofluorescent deposits at the dermal-epidermal junction (DEJ) of the skin (lupus band test or LBT) were evaluated in 134 patients with various connective tissue diseases. LBT was found positive in 23 of 32 (71.8%) patients with systemic lupus erythematosus (SLE), in 3 of 53 (5.6%) patients with rheumatoid arthritis (RA), and in 1 of 5 cases of mixed connective tissue disease (MCTD). No deposits were found in patients with systemic sclerosis and with vasculitis. In patients with SLE a positive LBT showed a direct correlation with serum Clq binding activity (ClqBA) and with hypocomplementemia. The mean ClqBA was 13.49 +/- 12.85 and 2.38 +/- 2.27% in SLE patients with positive and negative band test, respectively (P less than 0.005). Likewise depressed mean serum levels of C3 and C4 were detected in patients with skin deposits (P less than 0.005). Sera from SLE patients showed an overall decreased capacity to solubilize preformed immune complexes when compared to normal sera. Furthermore 10 band-positive patients were less able to solubilize immune complexes than sera from LBT-negative lupus patients (45 +/- 16 and 62 +/- 11%, respectively; P less than 0.01). Also the capacity to inhibit the precipitation of immune complexes was decreased in SLE patients with negative LBT (P less than 0.05). In conclusion our data suggest that in SLE patients a decreased complement-mediated solubilization of immune complexes is involved in the persistence of high levels of circulating immune aggregates and, considered its correlation with positive LBT, may be responsible for the deposits of immunoglobulins at the dermal-epidermal junction of the skin.

Adolescent↗
PubMedDate not supplied

Phylogeny of immune recognition: fine specificity of fish immune repertoires to cytochrome C.

Using the structurally defined protein antigen cytochrome C, studies were conducted in an attempt to delineate the fine specificities of channel catfish immune repertoires. We have previously reported that species variants of cytochrome C were cross-stimulatory to peripheral blood leukocytes (PBL) from catfish immunized with the pigeon variant. Molecular database analyses revealed the existence of overlapping epitopes that appear to define the specificity of the immune response to a "family" of closely related antigens. To further explore these observations, studies were conducted to determine the contribution of peptide 81-104 to the immunogenicity of cytochrome C. Current data showed that peptide 81-104 and intact cytochrome C were stimulatory to PBL from fish previously immunized with the native molecule. In contrast, PBL from fish previously primed with the peptide 81-104 responded only to the immunizing peptide as well as to some, but not all, variants of the peptide 81-104. The differences in the stimulatory capacities of the peptide variants appeared to correlate with amino acid substitutions at various positions of the peptide and changes in their predicted secondary structures.

Amino Acid Sequence↗
PubMed1979

Augmentation of the in vitro humoral immune response by pharmacologic agents. I: An explanation for the differential enhancement of humoral immunity via agents that elevate cAMP.

Agents that elevate intracellular concentrations of cAMP in cultured spleen cells can augment the in vitro 19s humoral immune response to SRBC. DBcAMP and 8BrcAMP were more effective than MIX, CT, PGE1, or ISO in producing the enhanced PFC response, when they were present only during an early stage of immune induction. The thesis is presented that the differential ability of these agents to augment humoral immunity results from their relative ability to maintain elevated concentrations of intracellular cAMP. Studies on the cellular mechanism by which cAMP elevation produces immune enhancement reveal that DBcAMP effects are on a T-cell-deficient population of murine spleen cells (predominantly B cells and macrophages). In addition, we showed that DBcAMP cannot replace the need for helper T cells in the induction of the PFC response to SRBC. Taken collectively, these results suggest that cAMP may be an important immunoregulatory signal, and that a variety of pharmacologic agents that modulate the induction of the humoral immune response may operate via this as a final common biochemical pathway.

1-Methyl-3-isobutylxanthine↗