Sera from patients with systemic lupus erythematosus reactive with human endothelial cells

Human endothelial cells (EC) cultured from umbilical cord veins were reacted with sera from patients with systemic lupus erythematous (SLE), rheumatoid arthritis (RA) and normal persons. Immunofluorescent staining for IgG, IgM and IgA was then performed. Two types of control cells were also used, human foreskin fibroblasts and KB cells (a human carcinoma cell line). Sera from 9 of the 18 (50%) SLE patients showed cytoplasmic staining of EC for IgG. KB cells and fibroblasts did not stain. None of the RA or normal sera showed positive staining. In the 9 instances in which there was positive staining, 4 had evidence of cutaneous vasculitis. In contrast, none of the 9 patients without EC cytoplasmic staining had clinical evidence of cutaneous vasculitis. This data suggests that some SLE patients have an IgG antibody that reacts with EC cytoplasm which may be related to cutaneous vasculitis.