[Pathogenesis of silicosis]

Up to now it has been assumed that quartz kills the macrophages, and that their disintegration releases a fibrogenic factor and antigens which induce the immune process causing the silicotic hyalines and other immune symptoms. According to new immunologic findings this theory is no longer tenable. A new hypothesis, complementary to that of Vigliani and Pernis in the 1960s, is that quartz and other fibrogenic dusts stimulate the macrophages, or their death is preceded by a period of stimulation. The stimulated macrophages release interleukin-1, a protein with a molecular weight of 15,000, which stimulates the production of fibroblasts and T-lymphocytes. The stimulated T-lymphocytes produce lymphokines and, in particular, the "macrophage Ia recruitment factor" (MIRF) which causes macrophages to produce Ia antigens. The Ia antigens are necessary for the macrophages' presentation of exogenous or endogenous antigens to the T-lymphocytes. The macrophages, additionally activated by the lymphokines, increase their immune functions so that a vicious circle macrophages/T-lymphocytes starts. The stimulated T-lymphocytes are now hyperactive against all T-dependent antigens, and their functions also include development of delayed hypersensitivity and action on the B-lymphocytes, inducing the latter's transformation into plasmoblasts and plasmocytes and the resultant production of gammaglobulins which precipitate locally on the collagen fibers.(ABSTRACT TRUNCATED AT 250 WORDS)