The effect of plasma exchange on the in vitro monocyte function of patients with immune complex diseases

In vitro function tests were performed on peripheral blood monocytes isolated from patients with putative immune complex diseases undergoing therapeutic plasma exchange. Bacterial killing by monocytes improved significantly after plasma exchange (pre: 29 +/- 5%; post: 39 +/- 3%). The intracellular content of the acid hydrolase N-acetylglucosaminidase (NAG) after in vitro culture rose significantly following plasma exchange (pre: 48.3 +/- 21 nmol mg protein-1 hr-1; post: 76.6 +/- 30.6), although the amount of NAG released into the supernatant was unchanged. Plasma exchange also resulted in reduced levels of immune complexes (IC) and clinical improvement in most patients. The beneficial effect of plasma exchange in patients with IC diseases may be partly due to removal of IC which are known to influence the functional activity of cells of the mononuclear macrophage series.