The occurrence and frequency of type C virus-like particles in placentas from patients with systemic lupus erythematosus and from normal subjects.

Type C RNA virus-like particles were found by electron microscopy in term placentas from 3 patients with systemic lupus erythematosus (SLE), 1 with probable SLE, and 2 normal patients. The virus-like particles were mainly of a budding or immature type located at or near the cell membrane of syncytiotrophoblasts in chorionic villi. Type C virus-like particles were not observed in the term placenta from a patient with chronic discoid LE, nor in early gestation specimens from 1 normal patient and 4 patients with SLE. The frequency of the Type C particles varied greatly: They were readily found in the patient with probable SLE, and only here were groups of budding particles observed. Type C particles were less numerous in one normal placenta and rare in the other positive placentas, both SLE and normal. Heretofore undescribed crystalline inclusions were found in the cytoplasm of chorionic villous endothelial cells from 3 patients with SLE and 1 with discoid LE. Tubuloreticular structures were observed in the maternal endometrium of 1 patient with SLE.