Location of T cell and major histocompatibility complex antigens in the human thymus.

Abstract

A series of monoclonal antibodies were used to study the intrathymic distribution of T cell-specific antigens, Ia antigens and .beta.2-microglobulin in frozen sections of human thymus by immunofluorescence and immunoperoxidase techniques. Most cortical thymocytes reacted with anti-T4, anti-T5, anti-T6, anti-T8 and anti-T10 antibodies, indicating coexpression of multiple antigens on cortical lymphocytes. The staining of cells in the medulla was most satisfactorily judged in sections stained with the immunoperoxidase technique. Many medullary cells reacted with anti-T4, and a smaller fraction with anti-T5, anti-T6, anti-T8 and anti-T10 antibodies. T1 and T3 antibodies, which react with all peripheral T cells, stained a majority of medullary cells. The medullary cells were more intensely stained with antibodies directed against .beta.2-microglobulin than the majority of cortical cells. The staining profile of medulla approximates the staining pattern of peripheral T cells, with large numbers of cells bearing T1+, T3+ and T4+ antigens (helper/inducer cells) and a small number of cells bearing T1+, T3+ and T5+/T8+ antigens (suppressor/cytotoxic cells). Apparently, mature cells present in the medulla are derived from immature cells in the cortex. A small number of cells scattered throughout the cortex stained with T1 and T3 antibodies, which suggests that thymocytes maturation can occur in the cortex. Antibody directed against Ia antigens resulted in a characteristic patchy pattern of staining in the cortex and in diffuse staining in the medulla, which was interpreted as resulting from staining of epithelial reticulum. Most thymocytes did not stain. The staining pattern suggests a close relationship between epithelial cells and thymocytes.