IN-VITRO INDUCTION OF PROINFLAMMATORY CYTOKINE SECRETION BY JUVENILE RHEUMATOID-ARTHRITIS SYNOVIAL-FLUID IMMUNE-COMPLEXES

Objective. To characterize juvenile rheumatoid arthritis synovial flui d (SF) immune complexes and to examine their interaction with leukocyt es. Methods. SF immunoglobulin-containing fractions were prepared by s equential chromatography on protein A and Sephacryl 300, Fractions wer e subdivided according to molecular weight, characterized for immunogl obulin and complement content, and incubated with either promonocytic U937 cells or normal human peripheral blood mononuclear cells (PBMC). Results. High molecular weight SF immunoglobulin-containing fractions stimulated the release of interleukin-1 beta (IL-1 beta) from U937 cel ls. These same complexes stimulated tumor necrosis factor alpha (TNF a lpha), IL-1 beta, IL-6, IL-8, and granulocyte-macrophage colony-stimul ating factor (GM-CSF) from PBMC, Lower molecular weight material was l ess efficient in inducing any of the cytokines, TNF alpha and IL-1 bet a were the earliest of the messenger RNAs examined to be induced by th e high molecular weight complexes, However, the secretion of IL-6, IL- 8, and GM-CSF stimulated by the complexes was not completely dependent upon the secretion of IL-1 beta, Addition of IL-1 receptor antagonist to the cell cultures reduced GM-CSF and IL-6 production by 40% and IL -8 production by 25% in PBMC. Conclusion. SF immunoglobulin fractions contain immune complexes that vary in size, composition, and phlogisti c potential, High molecular weight complexes are capable of inducing a spectrum of proinflammatory cytokines, all of which have been implica ted in the pathogenesis of rheumatic disease.