B-cell line-derived interleukin 1 is cytotoxic for melanoma cells and promotes the proliferation of an astrocytoma cell line.

We have previously described a unique molecular species of Interleukin 1 spontaneously produced by a human EBV-transformed B-cell line. This IL 1 shares a number of biological activities with monocytic IL 1 although its NH2-terminal amino-acid sequence is different from both IL 1 alpha and beta. In the present study we have investigated the activity of this B-cell IL 1 in two recently reported new assays for interleukin 1. We found that this B-cell IL 1 is able to promote the proliferation of the human astrocytoma cell line U373 in a dose dependent manner. We also describe that B-cell IL 1 is directly cytotoxic for a melanoma cell line, A375, but not for the tumor necrosis factor target cell, the murine transformed fibroblast line L929. These studies should prove useful in analysing structure-function relationships of the various IL 1 species, when the primary sequence of B-cell IL 1 becomes available.