Thymic shared antigen-2: A novel cell surface marker associated with T cell differentiation and activation

Abstract

Thymic shared Ag-2 (TSA-2) is a 28-kDa, glycophosphatidylinitosol-linked cell surface molecule expressed on various T cell and thymic stromal cell subsets. It is expressed on most CD3-CD4-CD8-, CD4+CD8+, and CD3highCD4-CD8+ thymocytes but is down-regulated on approximately 40% of CD3highCD4+CD8- thymocytes. Expression on peripheral TCR-alphabeta+ T cells is similar to that of CD3+ thymocytes, although a transient down-regulation occurs with cell activation. Consistent with the recent hypothesis that emigration from the thymus is an active process, recent thymic emigrants are primarily TSA-2-/low. TSA-2 expression reveals heterogeneity among subpopulations of CD3highCD4+CD8- thymocytes and TC..