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 CD3(high)CD4-CD8+ thymocytes but is down-regulated on ≃40% of CD3(high)CD4+CD8- thymocytes. Expression on peripheral TCR. αβ+ 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 CD3(high)CD4+CD8- thymocytes and TCR-γδ+ T ce..