Cytotoxic endothelial cell antibodies in mixed connective tissue disease

We examined the presence of anti-endothelial cell antibodies in the sera of 44 patients with mixed connective tissue disease (MCTD). Warm antibodies against endothelial cells were found in 45.4% of patients; the presence of these antibodies was positively correlated with anti-monocyte antibodies (P less than 0.01) but not with anti-lymphocytic antibodies. Strong correlations were found between the presence of these antibodies and abnormalities of pulmonary ventilatory capacity, neurophysiologic and myocardial function. Anti-endothelial antibodies were related to the high rate of spontaneous abortion noted in female MCTD patients. The identification of the antigen identified by MCTD sera in endothelial cells would help in understanding disease manifestations.