Electron microscopic study of distinctive structures in peripheral blood lymphocytes obtained from twins with systemic lupus erythematosus.

Peripheral blood lymphoid cells obtained from nine twin pairs (six monozygotic and three dizygotic) in which one or both twins had systemic lupus erythematosus (SLE) were examined by electron microscopy for the occurrence of two distinctive intracytoplasmic structures-tubuloreticular structures (TRS) and tubular crystalloids (TC). TRS were found in 0.8 to 14.8% of lymphoid-cell cross sections in 9 of 11 twins with SLE and 2 clinically well but serologically abnormal twins. Lymphoid cells of twins both clinically and serologically normal did not exhibit TRS, although their monozygotic or dizygotic SLE-positive counterparts possessed these structures. Thus, the expression of TRS was more consistent with an acquired than inborn trait and appeared to correlate with disease and serologic manifestations of SLE. TC were found in 1.7 to 7.9% of lymphoid-cell cross sections in every twin examined. No correlation was recognized between clinical or laboratory data and the frequency of TC-bearing cells. The significance and the ultrastructural development of TC in the peripheral blood lymphoid cells are briefly discussed.