Antigenic relationship between medullary thymocytes and a subpopulation of peripheral T cells in the rat: Description of a masked antigen

Abstract

Using differentially absorbed rabbit antisera to rat thoracic duct cells, an antigen is described which normally is expressed on the surface of T cells in thoracic duct lymph and lymph node, but which exists in a masked form on medullary thymocytes and apparently not at all on cortical thymocytes. This antigen is termed the rat masked thymocyte antigen (RMTA). RMTA on medullary thymocytes can be unmasked mechanically by sectioning in a cryostat or enzymatically by treating with neuraminidase. Trypsin destroys or removes RMTA. Nearly all the T cells in thoracic duct lymph and lymph node are RMTA +, whereas only 58–66% of T cells in spleen are RMTA +. RMTA + T cells, which are cortisone resistant, reside in the paracortex and periarteriolar sheath regions of lymph node and spleen. RMTA − T cells, which are cortisone sensitive, appear to reside in the red pulp of spleen. The results suggest that (i) two antigenically distinct populations of T cells exist in the rat, RMTA + and RMTA − T cells, (ii) medullary thymocytes are the immediate precursors of RMTA + T cells, and (iii) cortical thymocytes may be the immediate precursors of RMTA − cells.