Co-expression of mRNA for type I and type II interleukin-1 receptors and the IL-1 receptor accessory protein correlates to IL-1 responsiveness.

Three cell surface molecules participate in Interleukin-1 (IL-1) binding and signal generation, the two distinct types of receptors (type I IL-1R and type II IL-1R) and the IL-1 receptor accessory protein (IL-1RAcP). Low surface expression hampers the detection of all three components on a protein level in most cell types, thus the highly sensitive RT-PCR was used to analyse the mRNA expression in a panel of 18 murine cell types of different hemopoietic lineages and fibroblasts. The transcription of both types of IL-1 receptors was detected in all cell lines tested. In most cell lines the IL-1RAcP was co-expressed with the IL-1 receptors, and only these lines responded to IL-1. However, in three cell lines no mRNA for the IL-1RAcP could be detected, and these cells did not respond to IL-1. These results suggest that the expression of the IL-1RAcP correlates with IL-1 responsiveness and they point to a pivotal role for the IL-1RAcP in IL-1 signal generation.