Wayne R. Kindsvogel

IL-28, IL-29 and their class II cytokine receptor IL-28R

Cytokines play a critical role in modulating the innate and adaptive immune systems. Here, we have identified from the human genomic sequence a family of three cytokines, designated interleukin 28A (IL-28A), IL-28B and IL-29, that are distantly related to type I interferons (IFNs) and the IL-10 family. We found that like type I IFNs, IL-28 and IL-29 were induced by viral infection and showed antiviral activity. However, IL-28 and IL-29 interacted with a heterodimeric class II cytokine receptor that consisted of IL-10 receptor β (IL-10Rβ) and an orphan class II receptor chain, designated IL-28Rα. This newly described cytokine family may serve as an alternative to type I IFNs in providing immunity to viral infection.

TACI and BCMA are receptors for a TNF homologue implicated in B-cell autoimmune disease.

B cells are important in the development of autoimmune disorders by mechanisms involving disregulated polyclonal B-cell activation, production of pathogenic antibodies, and co-stimulation of autoreactive T cells. zTNF4 (BLyS, BAFF, TALL-1, THANK) is a member of the tumour necrosis factor (TNF) ligand family that is a potent co-activator of B cells in vitro and in vivo. Here we identify two receptors for zTNF4 and demonstrate a relationship between zTNF4 and autoimmune disease. Transgenic animals overexpressing zTNF4 in lymphoid cells develop symptoms characteristic of systemic lupus erythaematosus (SLE) and expand a rare population of splenic B-1a lymphocytes. In addition, circulating zTNF4 is more abundant in NZBWF1 and MRL-lpr/lpr mice during the onset and progression of SLE. We have identified two TNF receptor family members, TACI and BCMA, that bind zTNF4. Treatment of NZBWF1 mice with soluble TACI–Ig fusion protein inhibits the development of proteinuria and prolongs survival of the animals. These findings demonstrate the involvement of zTNF4 and its receptors in the development of SLE and identify TACI–Ig as a promising treatment of autoimmune disease in humans.

A soluble class II cytokine receptor, IL-22RA2, is a naturally occurring IL-22 antagonist.

IL-22 is an IL-10 homologue that binds to and signals through the class II cytokine receptor heterodimer IL-22RA1/CRF2–4. IL-22 is produced by T cells and induces the production of acute-phase reactants in vitro and in vivo, suggesting its involvement in inflammation. Here we report the identification of a class II cytokine receptor designated IL-22RA2 (IL-22 receptor-α 2) that appears to be a naturally expressed soluble receptor. IL-22RA2 shares amino acid sequence homology with IL-22RA1 (also known as IL-22R, zcytor11, and CRF2–9) and is physically adjacent to IL-20Rα and IFN-γR1 on chromosome 6q23.3–24.2. We demonstrate that IL-22RA2 binds specifically to IL-22 and neutralizes IL-22-induced proliferation of BaF3 cells expressing IL-22 receptor subunits. IL-22RA2 mRNA is highly expressed in placenta and spleen by Northern blotting. PCR analysis using RNA from various tissues and cell lines showed that IL-22RA2 was expressed in a range of tissues, including those in the digestive, female reproductive, and immune systems. In situ hybridization revealed the dominant cell types expressing IL-22RA2 were mononuclear cells and epithelium. Because IL-22 induces the expression of acute phase reactants, IL-22RA2 may play an important role as an IL-22 antagonist in the regulation of inflammatory responses.

Human cytokine receptor

Insults such as injury and infection call into play responses from a wide variety of cells and tissues. These include those immediately affected by, for example, a cut or abrasion, for example, the endothelium of blood vessels involved in local supply and leukocytes such as neutrophils, macrophages/ monocytes, lymphocytes, and platelets, which are, for the most part, recruited from the circulation after the initial insult and mediate local immune and inflammatory responses. In addition, trauma can involve tissues far from the immediate site(s) of damage; for example, the pattern of protein synthesis in the liver may alter toward acute-phase protein production and the hypothalarnus may be affected, generating systemic fever. It was long suspected that there might exist hormone-like molecules which acted as endogenous mediators of such immune and inflammatory responses, integrating the activities of widely scattered tissues. The example of endogeous pyrogen comes to mind (1). These ideas have been confirmed and extended in recent years by the isolation of cDNA clones for a number of such polypeptides. These are variously described as growth factors, cytokines, interleukins, interferons, and colony-

IL-21 mediates apoptosis through up-regulation of the BH3 family member BIM and enhances both direct and antibody-dependent cellular cytotoxicity in primary chronic lymphocytic leukemia cells in vitro

Interleukin-21 (IL-21) is a recently identified gamma-chain receptor cytokine family member that promotes B-cell apoptosis as well as activation of innate immune system. Based on this, we hypothesized that IL-21 might enhance the apoptosis induced by fludarabine and rituximab and also play a role in augmenting immune-mediated clearance of the chronic lymphocytic leukemia (CLL) cells. Our studies demonstrate that the majority of CLL patients have surface IL-21 receptor-alpha, and its expression correlates with apoptosis, tyrosine phosphorylation of STAT1, and up-regulation of the proapoptotic BH3 domain protein BIM. IL-21-induced BIM up-regulation is critical for apoptosis because inhibition of BIM expression using small interfering RNA prevented IL-21-induced apoptosis. IL-21 treatment of CLL cells but not normal T cells with fludarabine or rituximab additively enhanced the direct cytotoxic effect of these therapies. In addition to its proapoptotic effect, IL-21 promoted STAT1 and STAT5 phosphorylation in natural killer cells with concurrent enhanced antibody-dependent cellular cytotoxicity against rituximab-coated CLL cells in vitro. These data provide justification for combination studies of IL-21 with fludarabine and rituximab in CLL and suggest that BIM up-regulation might serve as relevant pharmacodynamic end point to measure biologic effect of this cytokine in vivo.

The Gly40Ser Mutation in the Human Glucagon Receptor Gene Associated With NIDDM Results in a Receptor With Reduced Sensitivity to Glucagon

The pancreatic islet hormone, glucagon, stimulates hepatic glucose production and has also been shown to potentiate glucose-induced insulin secretion. Because glucagon is a key regulator of glucose homeostasis, its receptor, which mediates the actions of glucagon, was considered a candidate gene involved in the pathogenesis of NIDDM. We have previously reported that a single heterozygous missense mutation in exon 2 of the glucagon receptor gene, which changes a glycine to a serine (Gly40Ser), is associated with NIDDM in a French population. In the present study, the signaling properties of this mutant receptor were examined in baby hamster kidney cells and rat insulinoma cells (REV-5AH) stably transfected with either the wild type or Gly40Ser mutant human glucagon receptor cDNAs. Competition assays using 125 I-labeled glucagon were performed, and in both cell types, the Gly40Ser mutant receptor was found to bind glucagon with an approximately threefold lower affinity compared with the wild type receptor. In both cell types, the production of cAMP in response to glucagon was decreased in cells expressing the mutant receptor compared with those expressing the wild type. Finally, glucagon-stimulated insulin secretion by RIN cells expressing the mutant receptor was decreased such that the dose-response curve was shifted to the right in comparison to that obtained with cells expressing the wild type receptor. These results indicate that this single-point mutation located in the extracellular region of the glucagon receptor decreases the sensitivity of target tissues to glucagon.

Differential effects of IL-2 and IL-21 on expansion of the CD4+ CD25+ Foxp3+ T regulatory cells with redundant roles in natural killer cell mediated antibody dependent cellular cytotoxicity in chronic lymphocytic leukemia.

CD4+ CD25+ regulatory T cells are expanded in solid and hematological malignancies including Chronic Lymphocytic Leukemia (CLL). Several cytokines and co-stimulatory molecules are required for generation, survival and maintenance of their suppressive effect. We and others have shown direct cytotoxic effect of the novel common gamma chain cytokine interleukin- 21 (IL-21) on primary B cells from CLL patients. Since members of this family of cytokines are known to exhibit their effects on diverse immune cells, we have examined the effects of IL-21 on CLL patient derived regulatory T cell induction, expansion and the inhibitory effect on natural killer cells in vitro. We demonstrate here the expression of IL-21 receptor in CD4+CD25High regulatory cells from CLL patients. In contrast to IL-2, the IL-21 cytokine failed to mediate expansion of regulatory T cells or induced expression of Foxp3 in CD4+CD25Intermediate or CD4+CD25Dim/- T cells in whole blood derived from CLL patients. Interestingly, in contrast to their differential effects on expansion of the CD4+CD25+Foxp3+T cells, IL-2 and IL-21 exhibited a redundant role in T-reg mediated suppression of NK cell mediated antibody dependent cytotoxicity function. Given the infusion related toxicities and pro-survival effect of IL-2 in CLL, these studies provide a rationale to explore IL-21 as an alternate gamma chain cytokine in CLL therapy.

Selective Regulation of CD8 T Cell Immune Function by IL-21 in HIV Infected Individuals

Background HIV infection is associated with skewed maturation of CD8 T cells, accumulation of cells in pre-effector stages and impaired effector function. Two g-chain signaling cytokines, IL-21 and IL-15, are known to enhance IFN-g in antigen-specific CD8T cells in humans and murine models and to synergize with each other. This study investigated IL-21 effects on CD8 T cells of HIV infected subjects.