In the present study we demonstrate that human monocytes activated by lipopolysaccharides (LPS) were able to produce high levels of interleukin 10 (IL-10), previously designated cytokine synthesis inhibitory factor (CSIF), in a dose dependent fashion. IL-10 was detectable 7 h after activation of the monocytes and maximal levels of IL-10 production were observed after 24-48 h. These kinetics indicated that the production of IL-10 by human monocytes was relatively late as compared to the production of IL-1 alpha, IL-1 beta, IL-6, IL-8, tumor necrosis factor alpha (TNF alpha), and granulocyte colony-stimulating factor (G-CSF), which were all secreted at high levels 4-8 h after activation. The production of IL-10 by LPS activated monocytes was, similar to that of IL-1 alpha, IL-1 beta, IL-6, IL-8, TNF alpha, granulocyte-macrophage colony-stimulating factor (GM-CSF), and G-CSF, inhibited by IL-4. Furthermore we demonstrate here that IL-10, added to monocytes, activated by interferon gamma (IFN-gamma), LPS, or combinations of LPS and IFN-gamma at the onset of the cultures, strongly inhibited the production of IL-1 alpha, IL-1 beta, IL-6, IL-8, TNF alpha, GM-CSF, and G-CSF at the transcriptional level. Viral-IL-10, which has similar biological activities on human cells, also inhibited the production of TNF alpha and GM-CSF by monocytes following LPS activation. Activation of monocytes by LPS in the presence of neutralizing anti-IL-10 monoclonal antibodies resulted in the production of higher amounts of cytokines relative to LPS treatment alone, indicating that endogenously produced IL-10 inhibited the production of IL-1 alpha, IL-1 beta, IL-6, IL-8, TNF alpha, GM-CSF, and G-CSF. In addition, IL-10 had autoregulatory effects since it strongly inhibited IL-10 mRNA synthesis in LPS activated monocytes. Furthermore, endogenously produced IL-10 was found to be responsible for the reduction in class II major histocompatibility complex (MHC) expression following activation of monocytes with LPS. Taken together our results indicate that IL-10 has important regulatory effects on immunological and inflammatory responses because of its capacity to downregulate class II MHC expression and to inhibit the production of proinflammatory cytokines by monocytes.

In this study it is shown that both membrane-bound and soluble forms of signaling lymphocytic activation molecule (SLAM) induce proliferation and Ig synthesis by activated human B cells. Activated B cells express the membrane-bound form of SLAM (mSLAM), the soluble (s) and the cytoplasmic (c) isoforms of SLAM, and the expression levels of mSLAM on B cells are rapidly upregulated after activation in vitro. Importantly, recombinant sSLAM and L cells transfected with mSLAM efficiently enhance B cell proliferation induced by anti-μ mAbs, anti-CD40 mAbs or Staphylococcus aureus Cowan I (SAC) in the presence or absence of IL-2, IL-4, IL-10, IL-12, or IL-15. sSLAM strongly enhances proliferation of both freshly isolated B cells and B cells derived from long-term in vitro cultures, indicating that SLAM acts not only during the initial phase of B cell activation but also during the expansion of preactivated B cells. In addition, sSLAM enhances production of IgM, IgG, and IgA by B cells activated by antiCD40 mAbs. SLAM has recently been shown to be a high affinity self-ligand, and the present data suggest that signaling through homophilic SLAM–SLAM binding during B–B and B–T cell interactions enhances the expansion and differentiation of activated B cells.

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BACKGROUND Cytokines play a key role in the regulation of cells of the immune system and also have been implicated in the pathogenesis of malignant diseases. Some cytokines have been shown to have potential in the diagnosis of cancer. METHODS A total of 111 patients with ovarian, cervical, or endometrial carcinomas or benign ovarian or uterine tumors were enrolled on the study, and the levels of interleukin (IL)‐2, IL‐4, IL‐6, IL‐10, interferon (IFN)‐γ, granulocyte‐colony stimulating factor (G‐CSF), granulocyte‐macrophage‐colony stimulating factor (GM‐CSF), macrophage‐colony stimulating factor (M‐CSF), and tumor necrosis factor (TNF)‐α were measured by cytokine specific, enzyme‐linked immunoadsorbent assays. In addition, ratios of IL‐2, IL‐4, and IFN‐γ production were studied to characterize the type of T‐cell response that occurred in the peritoneal cavities of the patients. RESULTS High levels of M‐CSF (mean for all patients, 26,050 pg/mL) and G‐CSF (mean for all patients, 20,267 pg/mL) were observed in virtually all patients, but no significant differences between the study groups were observed. Similarly, no differences in the levels of IL‐2, IL‐4, IL‐10, IFN‐γ, GM‐CSF, or TNF‐α were found. However, IL‐6 levels were significantly higher in patients with ovarian carcinoma (mean ± standard error of the mean [SEM]: 5572 ± 1266) or benign tumors (mean ± SEM: 4474 ± 2008) than in those with cervical (mean ± SEM: 1222 ± 546) or endometrial carcinoma (mean ± SEM: 1977 ± 616). A predominantly Th1 type cytokine profile, irrespective of the diagnosis, was observed in patients with gynecologic tumors. CONCLUSIONS With the exception of IL‐6, the cytokine synthesis profiles in the peritoneal fluids of patients with benign and malignant gynecologic tumors were found to be similar. These results suggest that cytokine production in these patients is a result of nonspecific inflammation rather than a specific response against the tumor cells, and that skewing of cytokine synthesis toward either the Th1 or the Th2 phenotype is not the underlying mechanism resulting in the malignant process in women with gynecologic tumors. Cancer 1998;83:788‐796. © 1998 American Cancer Society.

In the present study, the requirements and characteristics for the production of IL-13 by human T cells, T cell clones and B cells were determined and compared with those of IL-4. IL-13 was produced by human CD4+ and CD8+ T lymphocyte subsets isolated from peripheral blood mononuclear cells and by CD4+ and CD8+ T cell clones. CD4+ T cell clones belonging to Th0, Th1-like and Th2-like subsets produced IL-13 following antigen-specific or polyclonal activation. In addition, EBV-transformed B cell lines expressed IL-13 mRNA and produced small amounts of IL-13 protein. Expression of IL-13 mRNA and production of IL-13 protein by peripheral blood T cells and T cell clones was induced rapidly and was relatively long lasting, whereas IL-4 production by these cells was transient. In addition, IL-13 mRNA expression was induced by modes of activation that failed to induce IL-4 mRNA expression. IL-13 shares many biological activities with IL-4 which is compatible with the notion that the IL-13 and IL-4 receptors share a common component required for signal transduction. However, IL-13 lacks the T cell-activating properties of IL-4. Here we have shown that this is related to the fact that T cells fail to bind radiolabeled IL-13 and do not express the IL-13-specific receptor component. Taken together, these results indicate that the differences in expression and biological activities of IL-4 and IL-13 on T cells may have consequences for the relative roles of these cytokines in the immune response.