Secondary follicles in the thymus. Immunohistologic characterization of B lymphocytes using monoclonal antibodies

Studies were conducted into the incidence of secondary follicles in individuals without autoimmune disease. Thymic tissue specimens were obtained from 20 children, aged between 6 months and 14 years who had undergone cardiac surgery and had been chosen at random. These specimens were immunohistologically investigated, using monoclonal anti-B cell antibodies (CD19 to CD23, CD37) and anti-immunoglobulin antibodies. Follicular structures were found in 7 cases. They were localized in thymic medullary regions. Immunohistologically, the secondary follicles in the thymus exhibited staining patterns similar to those recordable from follicles in other lymphatic tissues, such as tonsils. Formation of follicular structures from the potential of normally detectable scattered B cells in the thymus appears to be quite common also in cases without autoimmune diseases.