Comparative study of the effect of chrysotile, quartz and rutile on the release of lymphocyte-activating factor (interleukin 1) by murine peritoneal macrophages in vitro.

The release of lymphocyte-activating factor (LAF) into the medium of cultured mouse resident peritoneal macrophages was estimated from the effect of this medium on the proliferation of mouse thymocytes in the presence of phytohaemagglutinin. Untriggered macrophages released little LAF into their culture medium. Upon addition of UICC chrysotile A (25-50 micrograms/10(6) macrophages), LAF appeared in the medium, and release continued for at least 20 h. DQ12 quartz was a more potent inducer of LAF production, while rutile was nearly inactive. Although chrysotile and quartz caused cell damage (as estimated by the release of lactate dehydrogenase), it was established that LAF release was not attributable to leakage of preformed intracellular LAF. The lymphoproliferative activity detected in macrophage media was stable at 56 degrees C and nondialysable, which corresponds to the properties of interleukin 1. These biochemical observations are consistent with the non-specific stimulation of the immune system found in asbestotic and silicotic patients.