Studies on endothelial cell cytotoxic activity in sera of patients with progressive systemic sclerosis, Raynaud syndrome, rheumatoid arthritis, and systemic lupus erythematosus.

Using human umbilical cord endothelial cell cultures and a modified 3HTdR uptake technique, endothelial cell cytotoxic activity (ECA) has been demonstrated in sera of 95/130 patients with progressive systemic sclerosis (PSS), 14/20 patients with Raynaud syndrome (RS), 52/153 rheumatoid arthritis (RA), and 47/113 systemic lupus erythematosus (SLE) sera. ECA could be enriched by gel filtration from PSS sera in a molecular weight range of 5 k daltons. ECA was partially associated with serum proteins, mainly in the albumin containing fraction, albeit at a lower level of activity. In PSS, no relationship of ECA to the type of skin involvement was observed. ECA appears to be a low molecular weight mediator of, as yet, unknown origin.