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M Kubin

Publications and source records attributed to M Kubin.

At least 37 records · Page 2Linked to original sources
PubMed1997

High level interleukin-12 production, but diminished interferon-gamma production, by cord blood mononuclear cells.

Cell-mediated immunity (CMI) in neonates is relatively deficient when compared with adults. Defects in cytokine production and/or regulation may contribute to heightened susceptibility to infection by intracellular pathogens. The heterodimeric cytokine IL-12 is a key regulator of CMI and inducer of interferon-gamma (IFN-gamma) production. We report here that umbilical cord blood-derived mononuclear cells (MNC) are capable of producing IL-12 (p40 subunit, measured by RIA, and IL-12 p70 heterodimer, by ELISA) at levels comparable to or greater than adult peripheral blood MNC, after stimulation with heat-killed Staphylococcus aureus in 18-h cultures. As in adult MNC, S. aureus induced IL-12 p40 mRNA accumulation in cord blood MNC. IFN-gamma was also produced in the S. aureus-stimulated cultures, in an IL-12-dependent manner, but cord blood MNC produced 5-fold lower levels of IFN-gamma compared with adult MNC (p < 0.05). Preincubation with IL-10 inhibited IL-12 p40 production by cord blood and adult peripheral blood MNC in a dose-dependent fashion, whereas neutralization of endogenous IL-10 enhanced IL-12 and IFN-gamma levels. The results demonstrate that the relative CMI deficiency in neonates is not due to an intrinsic defect in the capacity of neonatal MNC to produce IL-12. The underlying factors responsible for diminished IFN-gamma production are not known, but may lie in the balance of stimulatory and inhibitory signals delivered to the IFN-gamma secreting cells along with IL-12, or may relate more to the absence of memory T cells among cord blood MNC.

Fetal Blood↗
PubMed1996

The potential therapeutic role of interleukin-12 in cutaneous T-cell lymphoma.

Cutaneous T-cell lymphoma (CTCL) is a lymphoproliferative disorder characterized by skin invasion of clonally derived malignant CD4+ lymphocytes that phenotypically resemble mature T-helper (Th) cells. Sezary syndrome (SzS) represents an advanced form of CTCL associated with generalized erythroderma and involvement of the peripheral blood by the malignant cell population. We have previously demonstrated aberrant cytokine production by peripheral blood mononuclear cells (PBMCs) in SzS characterized by increased IL-4 and deficient IL-2 and IFN-gamma production, as well as increased expression of mRNA for IL-4 and IL-5 within active skin lesions, indicating that the clonal T-cell population is likely derived from the T-helper type 2 (Th2) subset of helper T lymphocytes. Furthermore, a variety of immune abnormalities have been observed in association with SzS that have been attributed to the cytokine abnormalities. Because IL-12 is a potent inducer of IFN-gamma production and causes the activation of cytotoxic lymphocytes, we assessed the production of IL-12 by PBMCs from SzS patients, and whether IL-12 could alter the unfavorable cytokine balance typical of SzS and, thus, possibly lead to correction of immune defects. In this review, we present our data, which indicate that patients with SzS exhibit marked defects in monocyte production of IL-12 p70. Moreover, in vitro culture of PBMC from SzS patients with recombinant IL-12 leads to reconstitution of normal IFN-gamma production and markedly enhances cell-mediated cytotoxicity.

Cells, Cultured↗
PubMed1996

Neutralization of IL-12 in vivo prevents induction of contact hypersensitivity and induces hapten-specific tolerance.

IL-12 is a heterodimeric cytokine with a powerful positive regulatory influence on the development of Th1 cell-mediated immune responses. Th1 cells are critically involved in contact hypersensitivity (CHS), so we were interested in studying whether IL-12 is of relevance in the induction phase of CHS. BALB/c mice were sensitized by epicutaneous application of 0.5% 2,4-dinitrofluorobenzene (DNFB) on the abdomen, draining lymph nodes obtained at various time points thereafter. RNA was extracted, and PCR analysis was performed using primers specific for the IL-12 subunits p35 and p40. Although p35 was constitutively expressed and not affected by hapten application, p40 transcripts were found to be enhanced in lymph nodes obtained between 12 and 24 h after sensitization. To study whether IL-12 is functionally relevant for the induction of CHS, an mAb directed against recombinant murine IL-12 was injected i.p. 3 and 24 h before sensitization. Challenge was performed 5 days later by painting the left ear with 0.3% DNFB. Whereas mice injected with sodium chloride or an isotype control Ab responded with a normal ear swelling after challenge with DNFB, mice treated with anti-IL-12 Ab showed a significantly reduced ear swelling response. To study whether injection of the IL-12 Ab causes transient nonresponsiveness or tolerance, resensitization was performed after a resting period of 14 days. Groups of mice initially treated with the anti-IL-12 Ab plus DNFB showed only a minimal response to DNFB after resensitization, suggesting that these mice became tolerant. Tolerance appeared to be hapten-specific because these mice could be successfully sensitized with the nonrelated hapten 2,4,6-trinitrochlorobenzene. Furthermore, when the anti-IL-12 Ab was injected into already sensitized mice before challenge, ear swelling response was significantly suppressed, suggesting that IL-12 also is involved in the effector phase of CHS. To exclude the possibility that the inhibitory effect of the anti-IL-12 Ab is simply due to an anti-inflammatory activity of the Ab, the anti-IL-12 Ab was injected i.p. 3 and 24 h before epicutaneous application of the toxic compound croton oil. However, irritant dermatitis elicited by croton oil was not affected by the Ab. Thus, the present study demonstrates that in vivo application of an anti-IL-12 Ab inhibits sensitization and induces hapten-specific tolerance and thus suggests that IL-12 may play a dominant in vivo role in the induction of CHS.

Animals↗
PubMed1996

IL-12 synthesis by human Langerhans cells.

IL-12 is a 70-kDa heterodimeric cytokine composed of a p35 chain and p40 chain. This cytokine exerts a powerful positive regulatory influence on the development of Th1 helper T-cell immune responses and is a potent inducer of IFN-gamma production and cytotoxic T cell differentiation and function. Because epidermal Langerhans cells (LC) are important members of the dendritic APC lineage family critical for initiating cell mediated immune responses, we examined LC for their ability to produce IL-12. Epidermal cell (EC) suspensions obtained from volunteers were enriched for, or depleted of, Langerhans cells (CD1a+ EC). Enriched populations contained > 90% CD1a+ cells, whereas depleted populations contained < 1% CD1a+ cells. As assessed by reverse transcription-PCR amplification, IL-12 p40 mRNA was constitutively expressed in LC RNA extracted immediately following keratome harvest, and increased spontaneously after overnight incubation. Radioimmunoassay (RIA) of IL-12 p40 protein on supernatants revealed IL-12 release by CD1a-enriched fractions of epidermal cells. Ab specific for p40 clearly demonstrated IL-12 in epidermal LC by flow cytometry. A bioassay for the functional IL-12 heterodimer (p70) indicated that LC could produce IL-12 biologic activity, which was neutralized by anti-IL-12 Ab. These results indicate that epidermal LC, in particular cultured LC maturing into dendritic cells, express IL-12 p40 mRNA, as well as p40 and functional p70 protein, and suggest that this is one mechanism behind the high potency of dendritic APCs, such as LC, to initiate Th1 type immune responses under appropriate conditions.

Adult↗
PubMed1996

IL-12 expression in AIDS-related lymphoma B cell lines.

IL-12 is a 70-kDa heterodimer formed by the 40-kDa heavy chain (p40) and the 35-kDa light chain (p35). Twenty-five Burkitt's lymphoma cell lines (CL) and seven normal lymphoblastoid B CL were studied. The Burkitt's CL included AIDS-associated B CL (AABCL) (7 EBV+/2 EBV-) and non-AABCL (8 EBV+/8 EBV-). Reverse transcription-PCR detected p40 in EBV+ AABCL (7 of 7), EBV+ non-AABCL (3 of 8), and normal lymphoblastoid B CL (6 of 6) but not in EBV- CL (0 of 10). p35 mRNA was detected in 30 of 30 CL. Constitutive secretion of p40 was found in 7 of 7 EBV+ AABCL (range, 341-18,086 pg/ml) and p70 in 3 of 7 EBV+ AABCL (range, 25-197 pg/ml), but in only 1 of 8 EBV+ non-AABCL and 0 of 7 normal lymphoblastoid CL. PMA stimulated p40 secretion in 7 of 7 EBV+ AABCL and p70 secretion in 5 of 7 EBV+ AABCL. PMA also triggered p40 and p70 secretion in 2 EBV+ non-AABCL and in 3 of 7 normal lymphoblastoid CL. No IL-12 secretion was detected in 10 EBV- CL, including EBV- AABCL. The CL produced IL-10, a known inhibitor of IL-12, but anti-IL-10 Abs did not neutralize IL-12. Similarly, neutralizing anti-IFN gamma Abs or IFN gamma did not affect B cell IL-12. For IL-12R studies, reverse transcription-PCR and 125I-IL-12 binding assays were performed. Although all CL tested showed mRNA accumulation for one of the IL-12R components, IL-12 binding sites were detected in only 1 of 30 CL. Our data suggest that: 1) AABCL constitutively secrete large amounts of IL-12, contrasting with low IL-12 production by HIV-1 infected PBMC; 2) lack of IL-12 expression in EBV- AABCL suggests that in vivo exposure of B cells to HIV-1 only does not induce IL-12 secretion and that both HIV-1 and EBV are required; 3) the autocrine-negative effect of IL-10 on IL-12 in monocytes and the enhancing effect of IFN gamma on IL-12 secretion do not apply to B cells derived from AIDS patients.

Acquired Immunodeficiency Syndrome↗
PubMed1996

Interleukin-12 prevents ultraviolet B-induced local immunosuppression and overcomes UVB-induced tolerance.

Ultraviolet (UV) light abrogates contact hypersensitivity (CHS) responses and induces hapten-specific tolerance. Because Th-1 cells are critically involved in CHS and are induced to develop by the cytokine interleukin (IL)-12, we asked whether IL-12 might overcome UV-induced local immunosuppression. C3H/HeN mice exposed to low doses of UV light over 4 d and hapten sensitized through the irradiated skin area with dinitrofluorobenzene showed profound inhibition of the CHS response, which was completely prevented upon intraperitoneal injection of murine recombinant IL-12 (rIL-12) after the last UV exposure. UV-treated mice resensitized 14 d after the first challenge displayed hapten-specific tolerance, whereas UV-exposed mice injected with rIL-12 before the first sensitization exhibited a vigorous CHS response. Furthermore, mice that were initially sensitized through UV-exposed skin also produced a significant CHS reaction when they received rIL-12 before resensitization. Adoptive transfer of spleen and lymph node cells from UV-irradiated mice treated with rIL-12 had no effect on the CHS response in recipient mice, whereas transfer of cells from UV-treated mice inhibited the immune response. These findings demonstrate that rIL-12 can prevent UV-induced local immunosuppression and overcome UV-induced hapten-specific tolerance.

Animals↗
PubMed1996

Peripheral blood mononuclear cells from autologous hematopoietic stem cell transplantation recipients produce and respond to IL-12.

Autologous hematopoietic stem cell transplantation effectively results in restoration of hematopoiesis, but induces an often prolonged period of T cell dysfunction including redistribution of T cell subsets and defective T cell proliferation. Because IL-2 production is markedly decreased following autologous stem cell engraftment, and because IL-12 has direct stimulatory effects on TH1 cells, a major source of IL-2, we investigated the production and responsiveness of IL-12 of peripheral blood mononuclear cells (PBMC) of autologous stem cell recipients in the first 6 months following engraftment. When stimulated with S. aureus Cowan I (SAC), PBMC from autologous hematopoietic transplant recipients in the early months following engraftment show no decrease in production of IL-12 as compared to control PBMC. Furthermore, transplant-derived PBMC appear to be functionally responsive to exogenously provided IL-12 as indicated by several criteria. In vitro proliferation of total PBMC and of isolated CD4+ T cells from transplanted recipients to PHA (1 microgram/ml) + IL-12 (20 U/ml) was comparable to controls, excluding the possibility that only NK or CD8+ cells respond to IL-12. Culture of both control and transplant-derived PBMC in PHA + IL-12 (20 U/ml) or IL-2 (100 U/ml) + IL-12 (20 U/ml) combinations yielded comparable production of IFN-gamma, one of the major biological effects of IL-12 in vivo, as well as equal production of TNF-alpha, a costimulatory factor of IL-12-mediated induction of IFN-gamma by NK cells. Taken together, this in vitro evidence suggests that following autologous transplantation, PBMC do not appear to have either decreased production of endogenous IL-12 or defective functional responsiveness to exogenously provided IL-12.

CD4-Positive T-Lymphocytes↗
PubMed1996

Serum interleukin-12 levels in patients undergoing allogeneic or autologous bone marrow transplantation.

Cytokines may be helpful in promoting hematopoietic reconstitution but have also an impact on the cellular interactions that contribute to GvHD and immunologic graft rejection. Because IL-12 is emerging as a central cytokine in immune response, we have investigated its levels in serum samples of patients undergoing bone marrow transplantation and transplant-related events. A double-antibody radioimmunoassay method for monitoring levels of endogenous IL-12, before and after allogeneic (27 patients) or autologous (19 patients) bone marrow transplantation, was used. The serum levels of IL-12 after allogeneic BMT were found to be relatively low (140-300 pg/ml) and similar to the IL-12 levels in the healthy donors (183 pg/ml). Seric IL-12 levels following autologous BMT (350 pg/ml) were higher than those observed in patients receiving an allogeneic BMT and in healthy donors. Our data indicate that the occurrence of GvHD and the development of infection after allogeneic BMT are not associated with IL-12 induction which suggests a possible down-regulation due to immunosuppressive treatment.

Adolescent↗
PubMed1995

Cytokine patterns during progression to AIDS in children with perinatal HIV infection.

Patterns of cytokine expression were analyzed in polyclonal and antigenic responses in children with perinatal HIV infection. Responses of PBL to PMA and A23187 calcium ionophore studied in patients in different stages of HIV infection revealed reduced levels of IL-2 in HIV-infected children beginning before 6 mo of age, and age-dependent increases in expression of IL-4, IL-10, and IFN-gamma. The levels of IL-4, IL-10, and IFN-gamma expression did not differ significantly between HIV-infected and age-matched uninfected children of HIV-seropositive mothers, except for a small reduction in HIV-infected children in late stages of infection. Responses to PHA, HLA alloantigens, HIV envelope peptides T1 and P18, and tetanus toxoid were studied in PBMC derived from asymptomatic and mildly symptomatic HIV-infected children. IL-2, IFN-gamma, IL-4, and IL-5 expression was detected in PHA-stimulated PBMC from all analyzed patients. HIV-infected children who failed to respond to HLA alloantigens, tetanus toxoid, or the envelope peptides had lower numbers of CD4+ cells and expressed, on PHA stimulation, higher levels of IL-4 and IL-5 and lower levels of IL-2 and IFN-gamma than patients who responded to the antigenic stimulation. Results of these analyses suggest that cytokine expression in HIV-infected children depends on the character of the stimuli as well as the phenotype of PBMC, and indicate possible prevalence of Th2 Ag-specific responses during the progression of HIV-induced immunodeficiency.

Acquired Immunodeficiency Syndrome↗
PubMed1995

IL-12 enhances Th1-type responses in human Leishmania donovani infections.

IL-12 is a pluripotent cytokine that interacts with NK and T cells to play a central role in the initiation and maintenance of Th1 responses and IFN-gamma production. Because of the interactive relationship between IL-12 and IFN-gamma response to infectious organisms, a study was undertaken to examine the role of IL-12 in the immune regulation of human visceral leishmaniasis (VL). Human (Hu) VL is associated with immune dysfunction and the appearance of IL-10 mRNA, not present in healed individuals. We found that PBMC from treated VL patients produced both IL-12 p40 and IFN-gamma in response to in vitro stimulation with Leishmania donovani. The production of both IL-12 p40 and IFN-gamma were interdependent and were abrogated by the addition of exogenous Hu rIL-10. In contrast, PBMC from active VL patients did not produce IL-12 p40 or IFN-gamma in response to L. donovani lysate. Neutralizing anti-IL-10 mAb led to the enhancement of IFN-gamma production by active VL PBMC cultured with L. donovani lysate, and this enhanced IFN-gamma production was blocked by anti-IL-12 mAb. The addition of exogenous Hu rIL-12 to PBMC from active VL patients resulted in the augmentation of IFN-gamma in response to L. donovani lysate. Therefore, treatment of active VL patient PBMC with anti-IL-10 or IL-12 shifted the response toward a Th1-type response with the production of IFN-gamma. These results indicate that IL-12 may play an important role in the regulation of the cellular immune responses in Hu VL.

Animals↗
PubMed1995

A recombinant Leishmania antigen that stimulates human peripheral blood mononuclear cells to express a Th1-type cytokine profile and to produce interleukin 12.

Leishmania braziliensis causes cutaneous and mucosal leishmaniasis in humans. Most patients with cutaneous leishmaniasis heal spontaneously and may therefore have developed protective immunity. There appears to be a mixed cytokine profile associated with active cutaneous or mucosal disease, and a dominant T helper (Th)1-type response associated with healing. Leishmanial antigens that elicit these potent proliferative and cytokine responses from peripheral blood mononuclear cells (PBMC) are now being identified. Herein, we report on the cloning and expression of a L. braziliensis gene homologous to the eukaryotic ribosomal protein eIF4A (LeIF) and patient PBMC responses to rLeIF. Patients with mucosal and self-healing cutaneous disease had significantly higher proliferative responses than those with cutaneous lesions. Whereas the parasite lysate stimulated patient PBMC to produce a mixed Th1/Th2-type cytokine profile, LeIF stimulated the production of interferon gamma (IFN-gamma), interleukin 2 (IL-2), and tumor necrosis factor alpha but not IL-4 or IL-10. Recombinant LeIF (rLeIF) downregulated both IL-10 mRNA in the "resting" PBMC of leishmaniasis patients and LPS-induced IL-10 production by patient PBMC. rLeIF also stimulated the production of IL-12 in cultured PBMC from both patients and uninfected individuals. The production of IFN-gamma by patient PBMC stimulated with either rLeIF or parasite lysate was IL-12 dependent, whereas anti-IFN-gamma monoclonal antibody only partially blocked the LeIF-induced production of IL-12. In vitro production of both IFN-gamma and IL-12 was abrogated by exogenous human recombinant IL-10. Therefore, we have identified a recombinant leishmanial antigen that elicits IL-12 production and Th1-type responses in patients as well as IL-12 production in normal human PBMC.

Animals↗
PubMed1995

IL-12 reverses cytokine and immune abnormalities in Sezary syndrome.

Cutaneous T cell lymphoma is a lymphoproliferative disorder typically characterized by skin invasion of clonally derived malignant CD4+ lymphocytes that phenotypically resemble mature Th cells. Sezary syndrome (SzS) represents an advanced form of cutaneous T cell lymphoma associated with generalized erythroderma and involvement of the peripheral blood by the malignant cell population. We have previously demonstrated aberrant cytokine production by PBMC in SzS characterized by increased IL-4 and deficient IL-2 and IFN-gamma production, as well as increased expression of mRNA for IL-4 and IL-5 within active skin lesions, suggesting that the clonal T cell population is derived from the Th 2 subset of helper T lymphocytes. These findings have been associated with a constellation of immune abnormalities that have been attributed to the cytokine abnormalities. Because IL-12 is a potent inducer of IFN-gamma production, and causes the activation of cytotoxic lymphocytes, we examined the production of IL-12 by PBMC from SzS patients and whether IL-12 could alter the unfavorable cytokine balance typical of SzS and thus lead to correction of immune defects. Despite normal numbers of peripheral blood monocytes and normal TNF-alpha production, mean Staphyloccus aureus and LPS-induced IL-12 p40 and p70 production by SzS PBMC was significantly decreased compared with PBMC from normal controls. Mean IFN-gamma production by patient PBMC in response to PHA alone was depressed, but increased to levels comparable with normal after addition of 1 ng/ml IL-12. Pretreatment of PBMC for 24 h with IL-12, IFN-alpha, or both together resulted in a decrease in PHA-stimulated IL-4 production from a base line of 1818 pg/ml to 1520, 1350, and 1058 pg/ml, respectively. Lastly, culture of patient PBMC with IL-12 for 24 h also resulted in significant increases in NK activity against K562 cells. These results indicate that PBMC from patients with SzS manifest a defect in IL-12 production and that the cytokine abnormalities associated with SzS can be favorably altered by IL-12.

Cytokines↗
PubMed1995

Interleukin-12 is required for interferon-gamma production and lethality in lipopolysaccharide-induced shock in mice.

Several cytokines, in particular tumor necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma), have been shown to be responsible for pathological reactions which may lead to shock and death observed in infection with Gram-negative bacteria and in response to endotoxins (lipopolysaccharides, LPS). Priming of mice with the avirulent Bacille Calmette Guérin (BCG) vaccine strain of Mycobacterium bovis increases the sensitivity of mice to the lethal effect of LPS and results in an efficient priming for cytokine production. In response to low doses (1 microgram/mouse) of LPS, BCG-primed mice produce interleukin-12 (IL-12) which controls IFN-gamma production, as demonstrated by the ability of neutralizing anti-IL-12 antibodies to suppress IFN-gamma production. However, the concentration of the biologically active IL-12 p70 heterodimer is similar in the serum of both BCG-primed or unprimed mice, reaching levels of 1-3 ng/ml at 3-6 h after LPS injection, whereas IFN-gamma production was observed only in BCG-primed mice. The priming effect of BCG on IFN-gamma production appears to be mostly due to its ability to increase TNF-alpha production, which acts as cofactor with LPS-induced IL-12 in inducing IFN-gamma production, as shown by the ability of injection of TNF-alpha and LPS (1 microgram/mouse), but not LPS alone, to induce IFN-gamma production. However, in addition to TNF-alpha, other LPS-induced cofactor(s) are required in cooperation with IL-12 to induce optimal IFN-gamma production, because co-injection of TNF-alpha and IL-12, sufficient to induce serum concentrations of both cytokines higher and more persistent than those obtained by injection of LPS, was not sufficient to induce IFN-gamma production in vivo. Neutralizing anti-IL-12 antibodies, in addition to inhibiting the in vivo LPS-induced IFN-gamma production, also completely protect BCG-primed mice injected with up to 10 micrograms of LPS from shock-induced death. Thus, IL-12 is required for IFN-gamma production and lethality in an endotoxic shock model in mice.

Animals↗
PubMed1994

IL-12 is expressed and released by human keratinocytes and epidermoid carcinoma cell lines.

IL-12 is a 70-kDa heterodimeric cytokine composed of two covalently linked chains, p40 and p35. IL-12 has multiple effects on T and NK cells and recently was found to be required for optimal Th1 cell development. In a variety of inflammatory skin disorders including delayed type hypersensitivity and contact hypersensitivity, Th1 cells appear to be critically involved. Because keratinocytes are well known to exhibit the capacity to release a variety of proinflammatory and immunologic cytokines, and thereby to be able to modulate inflammatory and immune reactions within the skin, it was investigated whether human keratinocytes and keratinocyte cell lines can release IL-12. Supernatants of phorbol-12,13-dibutyrate (PDBu) stimulated human epidermoid carcinoma cell lines (KB, A431) induced IFN-gamma production by PBL. This activity could be completely blocked by the addition of an anti-IL-12 Ab directed against the p40 subunit of IL-12 (C8.6). Release of IL-12 by keratinocyte cell lines was further confirmed by an RIA specific for p40. Immunoprecipitation under reducing conditions using the C8.6 Ab yielded specific bands at 40 kDa in supernatants of both KB cells and normal human keratinocytes. Northern blot analysis revealed IL-12-specific mRNA transcripts in PDBu-treated KB cells using cDNA probes encoding for p35 and p40. Moreover, by reverse transcription PCR specific transcripts for p35 and p40 were found in keratinocytes. These data indicate that keratinocyte cell lines and, although to a much lesser degree, normal human keratinocytes, exhibit the capacity to make IL-12; thus demonstrating for the first time IL-12 production by nonhemopoietic cells. Thus, one may speculate that keratinocytes via this capacity may influence the fate of Th-mediated immune responses, favoring Th1 responses by enhanced production of IL-12 or Th2 responses by reduced IL-12 release.

Base Sequence↗
PubMed1994

Interleukin 12 synergizes with B7/CD28 interaction in inducing efficient proliferation and cytokine production of human T cells.

Several receptors and counter-receptor pairs on T cells and on antigen-presenting cells (APCs) deliver costimulatory signals to T cells during antigen presentation. The CD28 receptor on T cells with its ligand B7 represents one of the best characterized and most important examples of this costimulation. We show here that interleukin 12 (IL-12), a cytokine also produced by APCs (monocyte/macrophages and B cells) and active on T and natural killer cells, has a strong synergistic effect with the B7/CD28 interaction in inducing proliferation and cytokine production in both mitogen-activated and freshly isolated peripheral blood T cells. Together with anti-CD28 antibodies, IL-12 induces proliferation of T cells to levels higher than those obtained with IL-2 stimulation and it is effective at IL-12 concentrations 100- to 1,000-fold lower than effective concentrations of IL-2. The proliferative effect of anti-CD28 and IL-12 is resistant to moderate doses of cyclosporin A and is largely independent of endogenous IL-2, IL-12, in synergy with anti-CD28 or B7-transfected cells, is most effective in inducing interferon gamma (IFN-gamma) production, but production of tumor necrosis factor alpha and granulocyte/macrophage colony-stimulating factor is also observed. IL-12-induced IFN-gamma production in peripheral blood mononuclear cells is inhibited by the chimeric molecule CTLA-4 immunoglobulin, which prevents binding of CD28 to B7, suggesting that endogenous B7 on the mononuclear cells and IL-12 cooperate in inducing IFN-gamma production. IL-10 inhibits both IL-12 production and B7 expression on monocytes. These two effects are largely responsible for the ability of IL-10, acting on accessory cells, to inhibit IFN-gamma production by lymphocytes, because anti-CD28 antibodies and IL-12 can reverse the inhibitory effect of IL-10 on IFN-gamma production. Our results in vitro suggest that the synergy between B7 and IL-12, a surface antigen and a soluble product of APCs, respectively, plays a role in regulating T cell activation and immune response in the microenvironment of inflamed tissues.

Animals↗
PubMed1994

Differential regulation of interleukin-12 (IL-12), tumor necrosis factor alpha, and IL-1 beta production in human myeloid leukemia cell lines and peripheral blood mononuclear cells.

Natural killer cell-stimulatory factor or interleukin-12 (NKSF/IL-12) was originally identified and purified from the conditioned medium of Epstein-Barr virus (EBV)-transformed B-cell lines. Phorbol diesters were observed to be potent stimulators of NKSF/IL-12 production from the B-cell lines. Although monocytes were found to be the major producers of NKSF/IL-12 in peripheral blood (PB) in response to lipopolysaccharide (LPS) or to Staphylococcus aureus, several myeloid leukemia cell lines tested did not produce detectable NKSF/IL-12 either constitutively or upon stimulation with phorbol diesters. However, three lines, ML-3, HL-60, and THP-1, responded to LPS with significant levels of NKSF/IL-12 production, whereas S aureus was effective only on THP-1 cells. When the cell lines were preincubated with compounds known to induce them to differentiate, production of tumor necrosis factor alpha (TNF alpha) and IL-1 beta was in most cases maximal in cells with differentiated characteristics, whereas NKSF/IL-12 production in response to LPS in all three producing cell lines was significantly enhanced only by pretreatment with dimethylsulfoxide (DMSO) for 24 hours, or by costimulation with interferon gamma (IFN gamma). The efficiency of DMSO enhancement of NKSF/IL-12 production decreased after 2 to 5 days of incubation, when the cells acquired differentiated characteristics. Unlike DMSO, IFN gamma enhanced NKSF/IL-12 production, and IL-10 and dexamethasone inhibited it in cell lines and PB mononuclear cells stimulated by either LPS or S aureus. The ability of the cell lines to respond to these mediators of possibly physiologically relevant function provides a tissue-culture model for studying their mechanism of action.

Animals↗