Cell Interleukin-2 Receptor Research Articles

Induction of IL-2 receptor expression and proliferation of T cell clones by a novel cytokine(s)

We found a unique T cell IL-2 receptor (IL-2R) 3 3 Abbreviations used: SN, supernatant; APC, antigen presenting cells; IL-2RIF, IL-2 receptor-inducing factor; Ab, antibody; OVA, ovalbumin; IL-2R, IL-2 receptor; rADF, recombinant ATL-derived factor; TCR, T cell receptor. -inducing activity in the supernatant (SN) of the TH1 clone stimulated with antigen on spleen cells as antigen-presenting cells (APC). We have tentatively named this activity the IL-2R-inducing factor (IL-2RIF) and have characterized the activity. The SN induced IL-2R and proliferation of TH1 clones stimulated with B cell APC, which could not induce IL-2R in the absence of the SN. Other known cytokines were examined for a IL-2RIF activity; however, none of cytokines examined exerted a similar activity. Moreover, the neutralizing antibodies against the known cytokines tested did not block the IL-2RIF activity in the SN. When TH1 clones were stimulated with immobilized anti-CD3 or with fixed B cell APC in the presence of partially purified IL-2RIF, these clones expressed IL-2R and showed IL-2-dependent proliferation, whereas they induced neither IL-2R expression nor proliferation in the absence of IL-2RIF activity. These observations suggest that IL-2RIF activity is mediated by a novel cytokine(s) and the cytokine plays an important role as a second signal in the activation of the TH1 clone.

Molecular regulation of hematopoietic cytokines: implications and indications for clinical use in pediatric oncology.

Proliferation and differentiation of hematopoietic progenitor cells are regulated by a network of stimulatory and inhibitory cytokines. An understanding of the molecular mechanisms of growth control may provide a physiologic basis for the innovative therapy of bone marrow disorders. Among various accessory cells, bone marrow T lymphocytes are capable of stimulating, as well as inhibiting, hematopoietic progenitor cells. We have now elucidated molecular mechanisms regulating the differential expression of T cell genes encoding for the stimulatory and inhibitory hematopoietic programs. Stimulation of hematopoiesis requires granulocyte-macrophage colony stimulating factor (GM-CSF), whereas inhibition requires interferon-gamma (IF gamma). Both cytokines can be induced by interleukin-2 (IL2). The T cell IL2 receptor consists of a 75 kD chain (p75) mainly expressed on a subset of resting T cells and a 55 kD chain (p55) which is strongly expressed upon T cell activation. P55 and p75 associate on activated T cells to form a dimeric receptor molecule exhibiting high affinity for IL2. The p75 monomer has an intermediate affinity for IL2. Expression of p55 in the context of the high affinity IL2 receptor constitutes a requirement for T cell IFg release. In contrast, p75 alone is capable of mediating the production of GM-CSF. Thus, T cells may be capable of selective production of cytokines with specific effects in hematopoietic growth control. Utilizing a human peripheral blood leukocyte genomic library, we identified various clones containing the entire GM-CSF gene, including coding and regulatory regions. Cloning of the GM-CSF gene allowed clinical studies utilizing recombinant DNA-derived GM-CSF. Chemotherapy-induced neutropenia contributes to both complications of cytotoxic therapy as well as increased relapse incidence of underlying disease. In a prospective randomized study, we have demonstrated that GM-CSF abrogates neutropenia following aplasiogenic chemotherapy in children and adolescents with solid tumors, and that GM-CSF may reduce the duration of infectious episodes after cytotoxic therapy. Next, we escalated the cumulative doses of cytotoxic therapy in an ablative regimen followed by hematopoietic stem cell transplantation to treat patients with poor prognosis pediatric tumors. Morbidity of this highly toxic ablative regimen depends on the duration of myeloid aplasia. Median duration of aplasia following hyper-VAMP was 13 days with CM-CSF and 29 days without GM-CSF. In addition, we have employed p55 blocking monoclonal antibody for prevention of graft vs. host disease in bone marrow transplantation. The understanding of specific molecular mechanisms of hematopoietic immuno-regulation can thus be utilized to provide novel approaches to the treatment of bone marrow failure and cancer.

A soluble form of the interleukin-1 receptor produced by a human B cell line

A soluble protein that binds specifically to interleukin-1 (IL-1)β was released from a B cell line (Raji). The covalently cross-linked binding protein/ [ 125I]IL-1β migrated at 60 kDa by SDS-PAGE. The IL-1 receptor (IL-1R) on Raji cells had the same ligand specificity. Stimulation of Raji with dexamethasone increased surface expression of the IL-1R and the rate of release of soluble binding protein. A serine protease inhibitor prevented release of the binding protein and increased IL-1R expression on the cells. These results suggest that the soluble IL-1β binding protein is a proteolytically cleaved form of the novel B cell IL-1R.

Both interleukin 2 and a second T cell-derived factor in EL-4 supernatant have activity as differentiation factors in IgM synthesis.

B cells cultured with anti-IgM, BSF-p1, and B15-TRF will differentiate into high rate IgM-synthesizing cells in the presence of supernatants from EL-4 cells that have been induced with phorbol myristate acetate. These supernatants contain two molecular species (EL-TRFs) that have differentiative activity. One co-migrates with interleukin 2 (IL-2) and its activity is blocked by antibody to the IL-2 receptor. Furthermore, molecularly cloned IL-2, at concentrations of 100 U/ml or more, expresses such EL-TRF activity. The EL-TRF activity of cloned IL-2 can also be inhibited by antibody to the IL-2 receptor. The other material with EL-TRF activity has a molecular weight of approximately 32,000. This material lacks IL-2 activity. Antibody to the IL-2 receptor does not impair its function. B cells stimulated with anti-IgM and BSF-p1, with or without B15-TRF, express determinants that react with two monoclonal antibodies which recognize distinct epitopes on the T cell IL-2 receptor. These determinants are present at much lower density (approximately 100-fold) on stimulated B cells that on HT-2 cells, an IL-2-dependent T cell line. Very small amounts of [3H]IL-2 (less than 1,000 molecules per cell) bind to activated B cells. These results indicate that IL-2 binds to a receptor on appropriately prepared B cells and causes them to differentiate into high rate IgM-synthesizing cells. The physiologic significance of the B cell differentiative activity of IL-2 remains to be investigated.