Polymorphonuclear functions in patients with mixed connective tissue disease.

Polymorphonuclear leukocytes (PMNs) from 29 patients with mixed connective tissue disease (MCTD) were studied "in vitro" for their phagocytic and chemotactic function as well as for granulocyte alkaline phosphatase (GAP) activity. Fc-receptor expression detected by EA-rosette formation was comparable to the control. Yeast-phagocytosis, C3b-receptor mediated phagocytosis and chemotaxis of PMNs, however, significantly decreased in MCTD. At the same time, photometric measure of alkaline phosphatase activity indicated a nearly two fold increase in PMNs from patients with MCTD. Although no correlation was found between PMN functions and the activity of the disease, PMN disorders may play a role in pathogenesis of these connective tissue disorders.