The occurrence of monocytoid B-lymphocytes in autoimmune disorders.

Occurrence of monocytoid B-lymphocytes (MBL) in extranodal organs in various inflammatory diseases was examined. MBL were present in 5 (11.4%) of 44 patients with Graves' disease, 11 (36.7%) of 30 with Hashimoto's thyroiditis, 1 (8.3%) of 12 with lymphoid follicular hyperplasia (LFH) of stomach, 1 (10%) of 10 with cutaneous LFH, and 0 of 5 with LFH of lung. The MBL presented as irregularly shaped nodular collections of cells, directly surrounding secondary follicles. Immunohistochemistry revealed a B-cell nature of these cells which expressed the following antigens; CD3-, CD 15-, CD45RA+, CD45Ro-, CDw 75+, CD74+, Mx-PanB+, MB-1+, EMA-. There were no immunoglobulin light chain restriction among infiltrating lymphoid cells. MBL in 2 of 18 cases showed positive reaction for CD43. The patients with MBL were older than those without MBL in each organ site, though the difference was not statistically significant. These findings showed that the MBL could appear in nonlymphoid organs affected by long-standing inflammation. High frequency of the appearance of the MBL in Hashimoto's thyroiditis suggest that MBL proliferation correlates with an impaired immune status.