The immunomodulatory effects of interferon-gamma on mature B-lymphocyte responses

Bioinformatics design of a peptide vaccine containing sarcoma antigen NY-SAR-35 epitopes against breast cancer and evaluation of its immunological function in BALB/c mouse model

The development of a cancer vaccine has become an essential focus in the field of medical biotechnology and immunology. In our study, the NY-SAR-35 cancer/testis antigen was targeted to design a novel peptide vaccine using bioinformatics tools, and BALB/c mice were used to evaluate the vaccine's immunological function. This evaluation involved assessing peptide-specific IgG levels in the serum via ELISA and measuring the levels of IFN-γ, IL-4, and granzyme B in the supernatant of cultured splenocytes. The final vaccine construct consisted of two T lymphocyte epitopes linked by the AAY linker. This construct displayed high antigenicity, non-allergenicity, non-toxicity, stability, and ability to induce IFN-γ and IL-4. It showed stable dynamics with both human MHC-I and II molecules, as well as mouse MHC-II molecules, and revealed strong Van der Waals and electrostatic energies. Emulsifying our peptide vaccine in incomplete Freund's adjuvant resulted in a remarkable increase in the levels of IgG. The splenocytes of mice that received the combination of peptide and adjuvant displayed a noteworthy increase in IFN-γ, IL-4, and granzyme B secretion. Additionally, their lymphocytes exhibited higher proliferation rates compared to the control group. Our data demonstrated that our vaccine could stimulate a robust immune response, making it a promising candidate for cancer prevention. However, clinical trials are necessary to assess its efficacy in humans.

Exercise-induced modulation of Interferon-signature: a therapeutic route toward management of Systemic Lupus Erythematosus

Systemic Lupus Erythematosus (SLE) is a multisystemic autoimmune disorder characterized by flares-ups/remissions with a complex clinical picture related to disease severity and organ/tissue injury, which, if left untreated, may result in permanent damage. Enhanced fatigue and pain perception, worsened quality of life (QoL) and outcome are constant, albeit symptoms may differ. An aberrant SLE immunoprofiling, note as "interferon (IFN)α-signature", is acknowledged to break immunotolerance. Recently, a deregulated "IFNγ-signature" is suggested to silently precede/trigger IFNα profile before clinical manifestations. IFNα- and IFNγ-over-signaling merge in cytokine/chemokine overexpression exacerbating autoimmunity. Remission achievement and QoL improvement are the main goals. The current therapy (i.e., corticosteroids, immunosuppressants) aims to downregulate immune over-response. Exercise could be a safe treatment due to its ever-emerging ability to shape and re-balance immune system without harmful side-effects; in addition, it improves cardiorespiratory capacity and musculoskeletal strength/power, usually impaired in SLE. Nevertheless, exercise is not yet included in SLE care plans. Furthermore, due to the fear to worsening pain/fatigue, SLE subjects experience kinesiophobia and sedentary lifestyle, worsening physical health. Training SLE patients to exercise is mandatory to fight inactive behavior and ameliorate health. This review aims to focus the attention on the role of exercise as a non-pharmacological therapy in SLE, considering its ability to mitigate IFN-signature and rebalance (auto)immune response. To this purpose, the significance of IFNα- and IFNγ-signaling in SLE etiopathogenesis will be addressed first and discussed thereafter as biotarget of exercise. Comments are addressed on the need to make aware all SLE care professional figures to promote exercise for health patients.

Ameliorative Effect of Imperatorin on Dermatophagoides pteronyssinus-Induced Allergic Asthma by Suppressing the Th2 Response in Mice

Imperatorin is a furanocoumarin derivative and an effective ingredient in several Chinese medicinal herbs. It has favorable expectorant, analgesic, and anti-inflammatory effects. In this study, we investigated whether imperatorin has protective effects against Dermatophagoides pteronyssinus (Der p)-induced asthma in mice. Lung and bronchial tissues were histopathologically examined through hematoxylin–eosin staining. The concentrations of immunoglobin E (IgE), IgG1, IgG2a in serum and those of T helper 1 (Th1) and two cytokines and eosinophil-activated chemokines in bronchoalveolar lavage fluid (BALF) were detected using an enzyme immunoassay. Histological examination revealed that imperatorin reduced inflammatory cell infiltration, mucus hypersecretion, and endothelial cell hyperplasia. The examination also indicated that imperatorin could reduce the inflammatory cell count in BALF as well as IgE and IgG1 expression in serum, but IgG2a expression was significantly increased. Imperatorin reduced the production of interleukin (IL)-4, IL-5, and IL-13 by Th2, promoted the production of interferon-γ and IL-12 by Th1, and increased the production of IL-10 in bronchoalveolar lavage fluid. These findings suggest that imperatorin has a considerable anti-inflammatory effect on Der p-induced allergic asthma in mice.

IFN-γ, should not be ignored in SLE

Systemic lupus erythematosus (SLE) is a typical autoimmune disease with a complex pathogenesis and genetic predisposition. With continued understanding of this disease, it was found that SLE is related to the interferon gene signature. Most studies have emphasized the important role of IFN-α in SLE, but our previous study suggested a nonnegligible role of IFN-γ in SLE. Some scholars previously found that IFN-γ is abnormally elevated as early as before the classification of SLE and before the emergence of autoantibodies and IFN-α. Due to the large overlap between IFN-α and IFN-γ, SLE is mostly characterized by expression of the IFN-α gene after onset. Therefore, the role of IFN-γ in SLE may be underestimated. This article mainly reviews the role of IFN-γ in SLE and focuses on the nonnegligible role of IFN-γ in SLE to gain a more comprehensive understanding of the disease.

OVA-Experienced CD4+ T Cell Transfer and Chicken Protein Challenge Affect the Immune Response to OVA in a Murine Model

Chicken meat is often a major component of a modern diet. Allergy to chicken meat is relatively rare and occurs independently or in subjects allergic to ovalbumin (OVA). We examined the effect of adoptive transfer of OVA-CD4⁺ T cells on the immune response to OVA in mice fed chicken meat. Donor mice were injected intraperitoneally with 100 µg of OVA with Freund’s adjuvant two times over a week, and CD4⁺ T cells were isolated from them and transferred to naïve mice (CD4⁺/OVA/ChM group), which were then provoked with OVA with FA and fed freeze-dried chicken meat for 14 days. The mice injected with OVA and fed chicken meat (OVA/ChM group), and sensitized (OVA group) and healthy (PBS group) mice served as controls. Humoral and cellular response to OVA was monitored over the study. The CD4⁺/OVA/ChM group had lowered levels of anti-OVA IgG and IgA, and total IgE. There were significant differences in CD4⁺, CD4⁺CD25⁺, and CD4⁺CD25⁺Foxp3⁺ T cells between groups. OVA stimulation decreased the splenocyte proliferation index and IFN-γ secretion in the CD4⁺/OVA/ChM group compared to the OVA group. IL-4 was increased in the OVA/ChM mice, which confirms allergenic potential of the egg–meat protein combination. Transfer of OVA-experienced CD4⁺ T cells ameliorated the negative immune response to OVA.

TCDD-mediated suppression of naïve human B cell IgM secretion involves aryl hydrocarbon receptor-mediated reduction in STAT3 serine 727 phosphorylation and is restored by interferon-γ

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a persistent environmental contaminant formed as a byproduct in organic synthesis and burning of organic materials. TCDD has potent immunotoxic effects in B lymphocytes resulting in decreased cellular activation and suppressed IgM secretion following activation with CD40 ligand. Previous work from our lab demonstrated that TCDD treatment of naïve human B cells resulted in significant increases in the levels of the tyrosine phosphatase SHP-1, which corresponded with suppression of IgM secretion. STAT3 is a critical B cell transcription factor for B cell activation and secretion of immunoglobulins (Ig). STAT3 dimerizes and translocates to the nucleus following phosphorylation as a result of cytokine receptor signaling. We hypothesized that TCDD-mediated increases in SHP-1 could result in decreased STAT3 tyrosine phosphorylation. Interestingly, only modest changes in the levels of STAT3 tyrosine phosphorylation were observed. By contrast, TCDD significantly reduced levels of STAT3 serine phosphorylation as early as 12h post B cell activation. These results corresponded with decreased inhibitory phosphorylation of the serine specific phosphatase PP2a, which is regulated by SHP-1. Further, studies revealed that interferon gamma (IFNγ), which signals through the type II interferon receptor, can non-canonically induce STAT3 activation via Src kinase activity. Indeed, treatment of human B cells with IFNγ resulted in increased STAT3 serine phosphorylation and reversed TCDD-mediated suppression of the IgM response. Together, these data putatively identify a key event in the mechanism by which TCDD induces suppression of Ig secretion and demonstrate the potential of IFNγ as a means to reverse this effect in primary human B lymphocytes.

Interferon γ and Its Important Roles in Promoting and Inhibiting Spontaneous and Therapeutic Cancer Immunity

Originally identified in studies of cellular resistance to viral infection, interferon (IFN)-γ is now known to represent a distinct member of the IFN family and plays critical roles not only in orchestrating both innate and adaptive immune responses against viruses, bacteria, and tumors, but also in promoting pathologic inflammatory processes. IFN-γ production is largely restricted to T lymphocytes and natural killer (NK) cells and can ultimately lead to the generation of a polarized immune response composed of T helper (Th)1 CD4+ T cells and CD8+ cytolytic T cells. In contrast, the temporally distinct elaboration of IFN-γ in progressively growing tumors also promotes a state of adaptive resistance caused by the up-regulation of inhibitory molecules, such as programmed-death ligand 1 (PD-L1) on tumor cell targets, and additional host cells within the tumor microenvironment. This review focuses on the diverse positive and negative roles of IFN-γ in immune cell activation and differentiation leading to protective immune responses, as well as the paradoxical effects of IFN-γ within the tumor microenvironment that determine the ultimate fate of that tumor in a cancer-bearing individual.

Submicroscopic Plasmodium infection during pregnancy is associated with reduced antibody levels to tetanus toxoid

Submicroscopic Plasmodium infections in pregnancy are common in endemic areas, and it is important to understand the impact of these low-level infections. Asymptomatic, chronic infections are advantageous for parasite persistence, particularly in areas where the optimal eco-epidemiological conditions for parasite transmission fluctuate. In chronic infections, the persistence of the antigenic stimulus changes the expression of immune mediators and promotes constant immune regulation, including increases in regulatory T cell populations. These alterations of the immune system could compromise the response to routine vaccination. This study aimed to evaluate the effect of submicroscopic plasmodial infection with P. falciparum and P. vivax during pregnancy on the immune response to the tetanus toxoid vaccine in Colombian women. Expression of different cytokines and mediators of immune regulation and levels of anti-tetanus toxoid (TT) immunoglobulin (Ig)G were quantified in pregnant women with and without submicroscopic plasmodial infection. The anti-TT IgG levels were significantly lower in the infected group compared with the uninfected group. The expression of interferon (IFN)-γ, tumour necrosis factor (TNF) and forkhead box protein 3 (FoxP3) was significantly higher in the infected group, while the expression of cytotoxic T lymphocyte antigen 4 (CTLA-4) and transforming growth factor (TGF)-β was lower in the group of infected. In conclusion, submicroscopic Plasmodium infection altered the development of the immune response to the TT vaccine in Colombian pregnant women. The impact of Plasmodium infections on the immune regulatory pathways warrants further exploration.

Role of nutrition, infection, and the microbiota in the efficacy of oral vaccines

Oral vaccines (OVs), provide protection against pathogens that infect mucosal surfaces and their potency relies on their capacity to elicit T- and B-cell responses directed to these surfaces. Oral vaccination efficacy has been found to vary considerably with differences in geographical locations and socioeconomic status. Specifically, in children living in resource-poor countries, undernourishment and chronic gastrointestinal (GI) infection are associated with the failure of OVs, which is a tragic outcome for the children who would benefit most from mucosal-based protection from infection. Both undernutrition and GI infection have been shown to profoundly affect the microbiota, inducing 'dysbiosis' characterized by narrowed bacterial diversity and increased frequency of bacterial clades associated with the induction of inflammation. Recent studies have demonstrated that the microbiota exerts a profound effect on the development of mucosal immune responses. Therefore, it seems likely that OV failure in resource-poor regions is affected by alterations to the immune response driven by dysbiotic changes to the microbiota. Here, we review the contribution of the microbiota to OV efficacy in the context of diet and GI infection.

IFNγ is Required for Optimal Antibody-Mediated Immunity against Genital Chlamydia Infection

Defining the mechanisms of immunity conferred by the combination of antibody and CD4⁺ T cells is fundamental to designing an efficacious chlamydial vaccine. Using the Chlamydia muridarum genital infection model of mice, which replicates many features of human C. trachomatis infection and avoids the characteristic low virulence of C. trachomatis in the mouse, we previously demonstrated a significant role for antibody in immunity to chlamydial infection. We found that antibody alone was not protective. Instead, protection appeared to be conferred through an undefined antibody-cell interaction. Using gene knockout mice and in vivo cellular depletion methods, our data suggest that antibody-mediated protection is dependent on the activation of an effector cell population in genital tract tissues by CD4⁺ T cells. Furthermore, the CD4⁺ T cell-secreted cytokine gamma interferon (IFN-γ) was found to be a key component of the protective antibody response. The protective function of IFN-γ was not related to the immunoglobulin class or to the magnitude of the Chlamydia-specific antibody response or to recruitment of an effector cell population to genital tract tissue. Rather, IFN-γ appears to be necessary for activation of the effector cell population that functions in antibody-mediated chlamydial immunity. Our results confirm the central role of antibody in immunity to chlamydia reinfection and demonstrate a key function for IFN-γ in antibody-mediated protection.

TLR3 and TLR9 agonists improve postexposure vaccination efficacy of live smallpox vaccines

Eradication of smallpox and discontinuation of the vaccination campaign resulted in an increase in the percentage of unvaccinated individuals, highlighting the need for postexposure efficient countermeasures in case of accidental or deliberate viral release. Intranasal infection of mice with ectromelia virus (ECTV), a model for human smallpox, is curable by vaccination with a high vaccine dose given up to 3 days postexposure. To further extend this protective window and to reduce morbidity, mice were vaccinated postexposure with Vaccinia-Lister, the conventional smallpox vaccine or Modified Vaccinia Ankara, a highly attenuated vaccine in conjunction with TLR3 or TLR9 agonists. We show that co-administration of the TLR3 agonist poly(I:C) even 5 days postexposure conferred protection, avoiding the need to increase the vaccination dose. Efficacious treatments prevented death, ameliorated disease symptoms, reduced viral load and maintained tissue integrity of target organs. Protection was associated with significant elevation of serum IFNα and anti-vaccinia IgM antibodies, modulation of IFNγ response, and balanced activation of NK and T cells. TLR9 agonists (CpG ODNs) were less protective than the TLR3 agonist poly(I:C). We show that activation of type 1 IFN by poly(I:C) and protection is achievable even without co-vaccination, requiring sufficient amount of the viral antigens of the infective agent or the vaccine. This study demonstrated the therapeutic potential of postexposure immune modulation by TLR activation, allowing to alleviate the disease symptoms and to further extend the protective window of postexposure vaccination.

IL-9 regulates allergen-specific Th1 responses in allergic contact dermatitis

The cytokine IL-9, derived primarily from T-helper 9 (Th9) lymphocytes, promotes expansion of the Th2 subset and is implicated in the mechanisms of allergic asthma. We hypothesize that IL-9 also has a role in human allergic contact dermatitis (ACD). To investigate this hypothesis, skin biopsy specimens of positive patch-test sites from non-atopic patients were assayed using quantitative PCR and immunohistochemistry. The cytokines IFN-γ, IL-4, IL-17A, IL-9, and PU.1, a Th9 associated transcription factor, were elevated when compared with paired normal skin. Immunohistochemistry on ACD skin biopsies identified PU.1+ CD3+ and PU.1+ CD4+ cells, consistent with Th9 lymphocytes, in the inflammatory infiltrate. Peripheral blood mononuclear cells from nickel-allergic patients, but not nonallergic controls, show significant IL-9 production in response to nickel. Blocking studies with mAbs to HLA-DR (but not HLA-A, -B, -C) or chloroquine significantly reduced this nickel-specific IL-9 production. In addition, blockade of IL-9 or IL-4 enhanced allergen-specific IFN-γ production. A contact hypersensitivity model using IL-9(-/-) mice shows enhanced Th1 lymphocyte immune responses, when compared with wild-type mice, consistent with our human in vitro data. This study demonstrates that IL-9, through its direct effects on Th1 and ability to promote IL-4 secretion, has a regulatory role for Th1 lymphocytes in ACD.

Therapeutic potential of Lactobacillus plantarum CJLP133 for house-dust mite-induced dermatitis in NC/Nga mice

Lactobacillus plantarum CJLP133 was isolated from Kimchi, a Korean fermented food, and its potential to improve mouse atopic dermatitis after onset was studied. Dermatitis was developed through house dust-mite extract application onto NC/Nga mice, and then CJLP133 feeding was started. CJLP133 suppressed dermatitis-like skin lesions and decreased high serum IgE levels through balancing between IL-4 and IFN-γ in serum. CJLP133 diminished skin thickening, mast cell accumulation into inflamed site, and lymph node enlargement. In lymph node cells, CJLP133 repressed secretion of T cell cytokines such as IFN-γ, IL-4, IL-5, and IL-10. However, CJLP133 decreased ratios of IFN-γ and IL-5 to IL-10 in lymph node cells, while it did not decrease ratios of IL-4 and IL-5 to IFN-γ. Conclusively, CJLP133 exhibited therapeutic potential for atopic dermatitis in mice through orderly increment of type 1 helper T cell activation and regulatory T cell activation. These results suggest that CJLP133 could treat human atopic dermatitis.

Evaluation of a recombinant BCG expressing antigen Ag85B and PPE protein Rv3425 from DNA segment RD11 of Mycobacterium tuberculosis in C57BL/6 mice

Antigen 85B (Ag85B) is an important immunodominant antigen of Mycobacterium tuberculosis, and is a very promising vaccine candidate molecule. Rv3425 is a member of the subgroup 3 of the PPE family, which does not exist in all BCG strains. In this study we constructed a new rBCG which included this united gene (Ag85B-Rv3425). The level of antigen-stimulated T cells expressing IFN-gamma was significantly higher in the C57BL/6 mice vaccinated with rBCG::Ag85B-Rv3425 than with BCG. In addition, the sera from mice immunized with rBCG::Ag85B-Rv3425 revealed an increase in the specific immunoglobulin G titers than that from mice immunized with BCG. Antigen specific IgG subclass analysis showed that rBCG::Ag85B-Rv3425 tended to facilitate IgG2a production, suggesting enhancement of predominant Th1 response which in turn may facilitate increased production of protective IFN-gamma. These results suggested that this rBCG::Ag85B-Rv3425 could be a strong vaccine candidate for further study.

Modulation of immune responses in mice to recombinant antigens from PE and PPE families of proteins of Mycobacterium tuberculosis by the Ribi adjuvant

Three proteins of PE and PPE families of Mycobacterium tuberculosis were evaluated for their ability to induce T cell responses in mice. To enhance immunity induced by protein immunization, we tested the efficacy of adjuvant Ribi (monophosphoryl lipid A+TDM), along with three proteins of the PE/PPE family. Balb/c mice were subcutaneously injected with recombinant proteins, encoded by Rv1818c, Rv3018c and Rv3812 genes of M. tuberculosis H37Rv, formulated with Ribi or IFA for comparative study. Sera from mice immunized with Ribi revealed an increase in the specific immunoglobulin G titers by twofold against Ribi than in mice immunized with IFA. Ribi also elicited stronger delayed-type hypersensitivity and cytotoxic T-lymphocyte activity against the recombinant proteins when compared with IFA. Antigen specific IgG subclass analysis showed that Ribi tends to facilitate IgG2a production, suggesting enhancement of predominant Th1 response which in turn may facilitate increased production of protective IFN-gamma. Furthermore, Ribi preparation increased the number of T cells secreting IFN-gamma. These results indicate that Ribi acts as an effective adjuvant for immune response to antigens of M. tuberculosis. For the first time, we demonstrate that Rv3018c, Rv1818c and Rv3812 proteins of PE/PPE family are T cell antigens with vaccine potential.

The tick salivary protein, Salp15, inhibits the development of experimental asthma

Activation of Th2 CD4(+) T cells is necessary and sufficient to elicit allergic airway disease, a mouse model with many features of human allergic asthma. Effectively controlling the activities of these cells could be a panacea for asthma therapy. Blood-feeding parasites have devised remarkable strategies to effectively evade the immune response. For example, ticks such as Ixodes scapularis, which must remain on the host for up to 7 days to feed to repletion, secrete immunosuppressive proteins. Included among these proteins is the 15-kDa salivary protein Salp15, which inhibits T cell activation and IL-2 production. Our objective for these studies was to evaluate the T cell inhibitory properties of Salp15 in a mouse model of allergic asthma. BALB/cJ mice were Ag sensitized by i.p. injection of OVA in aluminum hydroxide, with or without 50 mug of Salp15, on days 0 and 7. All mice were challenged with aerosolized OVA on days 14-16 and were studied on day 18. Compared with control mice sensitized with Ag, mice sensitized with Ag and Salp15 displayed significantly reduced airway hyperresponsiveness, eosinophilia, Ag-specific IgG1 and IgE, mucus cell metaplasia, and Th2 cytokine secretion in vivo and by CD4(+) T cells restimulated with Ag in vitro. Our results demonstrate that Salp15 can effectively prevent the generation of a Th2 immune response and the development of experimental asthma. These studies, and those of others, support the notion that a lack of ectoparasitism may contribute to the increasing prevalence of allergic asthma.

Pseudo-rationale design of efficient TB vaccines: Lesson from the mycobacterial 27-kDa lipoprotein

To develop or improve acellular vaccines against tuberculosis, scientists are in quest for the most efficient Th1 antigens. Immunization of mice with the M. tuberculosis 27-kDa antigen resulted in a strong Th1 immune response as indicated by serum analysis, splenocyte proliferation and cytokines secretion profile. Unexpectedly, mice immunized with 27-kDa turned out to be more susceptible to mycobacterial challenge as we found significant increase in the splenic cfu count compared to control groups. Moreover, the protection provided by BCG or other mycobacterial antigens was completely abolished once the 27-kDa antigen was added to the vaccine preparations. Further analysis of 27-kDa revealed that this lipoprotein is a B-cell mitogen, a feature that is known to be linked to enhanced virulence of the pathogen. However, by using the non-acylated form, 27DeltaSP, we excluded the involvement of the mitogenicity of 27-kDa in its deleterious effect. Currently, there is no explanation to the fact that the 27-kDa interferes with the protective immunity of other mycobacterial antigens; however, it is clear that 27-kDa need to be excluded from any future vaccine preparations. Indeed, we developed a multivalent vaccine that consists of six other mycobacterial antigens: 85B, 38-kDa, ESAT-6, CFP21, Mtb8.4 and 16-kDa. Immunization of mice with these antigens emulsified in Ribi adjuvant system and supplemented with recombinant IFN-gamma, resulted in strong Th1 immune response and a high protection level that was comparable to that of BCG.

Topical Imiquimod Treatment Prevents UV-Light Induced Loss of Contact Hypersensitivity and Immune Tolerance

Imiquimod (1-(2-methylpropyl)-1H-imidazo[4,5-c]quinolin-4-amine) is a TLR7 agonist that induces cytokine production in TLR7 bearing antigen-presenting cells (APCs), including IL-12, a cytokine that has been demonstrated to be a critical effector molecule for contact hypersensitivity (CHS). To test our hypothesis that topical applications of imiquimod may protect the skin immune system against the deleterious effects of UV light exposures, we treated animals with this agent, or its vehicle or nothing before UV exposures. Although topical imiquimod exposures before UV light did not prevent the depletion of epidermal Langerhans cells, it did prevent the loss of CHS. IL-12 was important in the protective role of imiquimod in preventing UV-induced loss of CHS, as systemic treatment of mice with an anti-IL-12 p70 monoclonal antibody blocked the protective effects of imiquimod. Additionally, only imiquimod-treated mice were resistant to hapten-specific tolerance induction after UV irradiation at the site of the initial sensitization with the hapten 2,4 dinitro-1-fluorobenzene. To model for the effects of TLR7 activation on the UV effect on antigen-APCs, XS52 cell line was used to study this interaction in an in vitro model system. This cell line expressed mRNA for TLR7, downregulated IkappaB, phosphorylated c-Jun N-terminal kinase, and secreted cytokines after exposure to imiquimod or lipopolysaccharide. Activation of the TLR7 signaling pathway on XS52 before UV-light exposures enhanced IL-12p70 secretion by this cell line. Similarly, activation of TLR7 on XS52 before UV-light exposure also prevented the UV-induced loss of IFN-gamma triggering in T cells during an allogeneic mixed lymphocyte reaction. Imiquimod-treated, UV-irradiated XS52 triggered a more vigorous IFN-gamma production than did either imiquimod-treated XS52 or UV-irradiated XS52, again suggesting a synergy between the two treatments. Lastly, enriched lymph node CD11c+ APCs from mice treated with UV irradiation, imiquimod alone or the combination of UV irradiation and imiquimod indicated the same in vivo synergy between imiquimod irradiation and UV irradiation in enhancing IL-12p70 production. These data suggest that topical imiquimod applications may play a role in preventing UV-induced impairment of the skin immune system, which is thought to be one of the critical events that allow the development of UV-induced skin cancers.

Gamma interferon and monophosphoryl lipid A-trehalose dicorynomycolate are efficient adjuvants for Mycobacterium tuberculosis multivalent acellular vaccine

In this study, we examined the immunogenicity and protective efficacy of six immunodominant Mycobacterium tuberculosis recombinant antigens (85B, 38kDa, ESAT-6, CFP21, Mtb8.4, and 16kDa) in a multivalent vaccine preparation (6Ag). Gamma interferon (IFN-gamma) and monophosphoryl lipid A-trehalose dicorynomycolate (Ribi) adjuvant systems were used separately or in combination for immunization with the recombinant antigens. Our results demonstrate that immunization of mice with Ribi emulsified antigens in the presence of IFN-gamma (Ribi+6Ag+IFN-gamma) resulted after challenge with a virulent M. tuberculosis strain in a significant reduction in the CFU counts that was comparable to that achieved with the BCG vaccine ( approximately 0.9-log protection). Antigen-specific immunoglobulin G (IgG) titers in the Ribi+6Ag+IFN-gamma-immunized mice were lower than in mice immunized with Ribi+6Ag and were oriented toward a Th1-type response, as confirmed by elevated IgG2a levels. In addition, splenocyte proliferation, IFN-gamma secretion, and NO production were significantly higher in splenocytes derived from Ribi+6Ag+IFN-gamma-immunized mice, whereas IL-10 secretion was decreased. These findings confirm the induction of a strong cellular immunity in the vaccinated mice that correlates well with their enhanced resistance to M. tuberculosis. The adjuvant effect of IFN-gamma was dose dependent. A dose of 5 mug of IFN-gamma per mouse per immunization gave optimal protection, whereas lower or higher amounts (0.5 or 50 mug/ mouse) of IFN-gamma failed to enhance protection.

Trypanosoma cruzi-induced decrease in the level of interferon-gamma receptor expression by resting and activated human blood lymphocytes

A substantial proportion of human peripheral blood mononuclear cells (PBMC) manifested a decreased capacity to express membrane interferon-gamma receptors (IFN-gamma R) when co-cultured with Trypanosoma cruzi. Among the lymphocytes, B cells accounted for the bulk of this effect, evidenced by a marked drop in the proportion of CD19+ or CD20+ cells expressing IFN-gamma R. Decreased IFN-gamma R expression by B lymphocytes was seen as early as 3 h after co-culture with T. cruzi and persisted for at least 24 h. The parasite had no detectable effect on CD19, CD20 or DR antigen expression by B lymphocytes. Neither the proportion of B cells expressing these markers nor the membrane density of these molecules varied significantly in the presence of T. cruzi. In PBMC cultures stimulated with Staphlyococcus aureus Cowan I (SACI), T. cruzi decreased the percentages of both IFN-gamma R+ and IFN-R+bright (cells expressing above-normal levels of surface IFN-gamma R) B lymphocytes. Cell-free filtrates of T. cruzi suspensions reproduced the suppressive effects of living parasites on IFN-gamma R expression by B cells. When T. cruzi present, the intracellular levels of IFN-gamma R molecules in resting or SACI-activated B lymphocytes, represented by fluorescence intensity, were well below control values, suggesting that decreased surface expression resulted from suppressed IFN-gamma R synthesis. Among T (CD3+) cells, 10.8% to 39.6% (7 donors) expressed surface IFN-gamma R and did so at a very low level. These percentages were also reduced by T. cruzi.(ABSTRACT TRUNCATED AT 250 WORDS)

IFN-gamma enhances secretion of IgG2a from IgG2a-committed LPS-stimulated murine B cells: implications for the role of IFN-gamma in class switching

IFN-gamma is a pleiotropic lymphokine that influences the isotypes of immunoglobulin secreted by B cells. IFN-gamma inhibits the secretion of IgG3, IgG2b, IgG1, and IgE, and enhances the secretion of IgG2a. We have examined the mechanism of IFN-gamma-mediated enhancement of IgG2a secretion in sorted populations of B cells and find that IFN-gamma reproducibly stimulates a twofold increase in the precursor frequency of IgG2a-secreting cells in the sIgG2a+ population. Additionally, we find that IFN-gamma does not induce an increase in the clone size of IgG2a-secreting cells. IFN-gamma stimulates a twofold increase in the precursor frequency of IgG2a-secreting cells from sIgG- and unsorted B cells which can be attributed to an increase in IgG2a secretion from IgG2a-committed cells in these populations. Hence, under the culture conditions utilized in these studies. IFN-gamma enhances IgG2a secretion from IgG2a-committed cells and does not induce a class switch.