Thymic reticulum of autoimmune mice. II: Ultrastructural studies of mice with lupus-like syndrome (NZB, BXSB, MRL/l).

We examined the thymic reticulum of three strains of mice showing symptoms of lupus-like disease. Ultrastructural pathology revealed several features common to the three mouse strains in varying degrees according to sex and age of the mice. Main anomalies included vacuolized aspect of the thymic epithelium, an increased number of macrophages, interdigitating cells and cystic cavities, the presence of a great number of plasmocytes and mastocytes and extensive interstitial fibrosis and arteriosclerosis. The most intriguing finding was the presence of crystal-like inclusions in epithelial cells. Some thymuses also showed premature histologic modifications similar to those observed in the ageing involuted thymus. Dysfunction of the epithelial cell secretory system, accumulation of denatured thymic hormone as well as premature organ ageing associated with a loss of thymic function could contribute significantly to the autoimmune phenomenon observed in lupus mice.