Molecular heterogeneity of interleukin-1 receptors

Previous studies have shown that binding of IL-1 to its receptor and intracellular processing of the IL-1/IL-1 receptor complex appear to be different in B- and T-cells. The current report summarizes recent studies from our laboratory that show that the murine and human IL-1 receptors present on T-cells and fibroblasts are identical in primary sequence within each species, and highly similar even when the two species are compared. At present no cDNA clones have been isolated for IL-1 receptors present on B-cells. However, a monoclonal antibody raised to the receptor on murine T-lineage cells did not bind to a pre-B-lymphoma cell line that displays IL-1 binding sites, nor would cDNA probes derived from a T-cell IL-1 receptor clone cross hybridize at high stringency to mRNA prepared from these cells. In addition the two receptors differ substantially in size, as determined by affinity crosslinking with radiolabeled IL-1 alpha. Taken together, these observations show that major structural differences exist between the IL-1 receptors on B and T lymphocytes, while the receptors on T-cells and fibroblasts are identical polypeptides. We propose that the T-cell/fibroblast receptor be called IL-1RI and the B-cell type IL-1RII.