The combination of IL-1 and IL-4 stimulates the proliferation of certain murine T cell populations. Although this effect has been best characterized for a number of murine type 2 Th cell (Th2) clones, the mechanism(s) by which these cytokines effect this response is unclear. We have examined the effects of IL-1 and IL-4 on IL-1R expression by MD10 cells, and IL-1-responsive murine T cell line. These cells bear specific IL-1R, which bind human and murine IL-1 alpha and -beta. The measured apparent IL-1R dissociation constant ranged from 41 to 255 pM using 125I-HrIL-1 alpha. Cross-linking studies demonstrated two different 125I-HrIL-1 alpha binding complexes having Mr of 70,000 and 130,000 to 156,000. When removed from passage conditions and placed in non-growth factor-supplemented media, MD10 IL-1R expression spontaneously increased two- to fourfold over the first 11 to 12 h of culture followed by a decline. This phenomenon is partially inhibitable by cycloheximide suggesting that protein synthesis is involved. In agreement with other reports, HrIL-1 alpha down-regulated the expression of its own receptor with an ED50 of between 1 and 10 pM HrIL-1 alpha for this effect. In most experiments, low amounts of HrIL-1 alpha (1.0, 0.1 pM) significantly augmented IL-1R expression. Scatchard analysis of data obtained with all HrIL-1 alpha treatment conditions showed that the effects were due to a change in receptor number, not affinity. Significantly, purified murine IL-4 (MpIL-4) augmented MD10 IL-1R expression in both a time- and dose-dependent fashion. In the presence of 50 U/ml MpIL-4, MD10 IL-1R expression increased two- to threefold after 24 h without a change in receptor affinity. When MpIL-4 (50 U/ml) and various amounts of HrIL-1 alpha (.01-1000 pM) were co-added, the down-regulatory effect of high levels of HrIL-1 alpha was significantly antagonized. When added to cultures after 24 h of HrIL-1 alpha (100 pM) treatment, MpIL-4 reversed the IL-1R down-regulatory effect induced by high levels of HrIL-1 alpha. Finally, when combined in MD10 proliferation assays, MpIL-4 synergistically enhanced the proliferation of MD10 cells treated with suboptimal levels of HrIL-1 alpha.(ABSTRACT TRUNCATED AT 400 WORDS)

Although interleukin (IL) 2-responsive T cell lines provide an opportunity to study the cellular effects of this lymphokine on homogeneous T lymphocyte populations, T cell clones which proliferate in response to IL-1 alone have not been available. We have isolated from cultures of the nontransformed murine T helper cell line, D10 . G4 . 1, a variant (MD10 cells) which proliferates (no lectin or antigen needed) in response to IL-1 alone. The MD10 cells are markedly sensitive to either murine or human recombinant IL-alpha (HrIL-1 alpha) with half-maximal responses observed at monokine concentrations as low as 0.4 X 10(-12) M or 0.8 U/ml, respectively. MD10 cells show the maximal IL-1 effect at 72 hr where the response exceeds the base line by 100-fold (approximately 3,000----300,000 cpm of [3H]thymidine). Whereas both HrIL-2 and purified murine B cell-stimulatory factor 1 (MpBSF-1) induce MD10 proliferation, the maximal response to either is much lower (HrIL-2: 50X baseline; MpBSF-1: less than 20X base line) than to IL-1. Conditioned media from control, concanavalin A-, or IL-1-treated MD10 cells fail to stimulate CTLL or HT-2 cell proliferation alone or inhibit CTLL mitogenesis in the presence of added HrIL-2. Furthermore, monoclonal antibodies to BSF-1 fail to inhibit IL-1-stimulated MD10 replication, and neither HT-2 nor CTLL cells proliferate despite direct cell-to-cell contact with IL-1-treated MD10 cells. When combined, IL-1 (10(-13), 10(-12) M) and IL-2 (10(-13) to 10(-10) M) act synergistically in their MD10 cell growth-promoting effects. MD10 proliferation induced by either IL-1 or IL-2 is relatively resistant to cyclosporine A, with the ID50 of cyclosporine for both IL-1- and IL-2-exposed MD10 cells (ID50 5000 ng/ml) exceeding that for concanavalin A-activated splenocytes (ID50 20 ng/ml) by 2 to 3 orders of magnitude. Finally, MD10 cells bear the L3T4 antigen, IL-2 receptors, and the same clonotypic antigen receptor as the parent clone as recognized by monoclonal antibody 3D3. These data suggest that, in respect to this particular T cell line, IL-1 is directly growth-promoting or, alternatively, induces the production of undetectable, intermediate growth factor(s) resistant to inhibition by cyclosporine A.