Recent studies have demonstrated that CD3 is expressed on a subset of thymocytes with a CD4-CD8- (double negative) phenotype1,2. At least some of these cells bear the CD3-associated γδ T-cell receptor (TCR γδ)3,4. Here we describe a second subset of double negative thymocytes which expresses CD3-associated αβ receptors (TCR αβ). Surprisingly, these cells express predominantly the products of a single Vβ; gene family (Vβ8). These CD4-CD8-, TCRαβ+ cells appear relatively late in ontogeny (between birth and day 5 of life) and thus are unlikely to be the precursors to the TCR αβ-bearing cells (CD4+CD8- and CD4 -CD8+) already present at birth. They can be selectively expanded in vitro by stimulation with a monoclonal antibody to V β8 (F23.1)5 in the presence of interleukin I (IL-1). We propose that this cell type is a unique T-cell population distinguishable from typical TCR αβ+ T cells by its CD4 -CD8- phenotype and a restricted TCR Vβ repertoire. Analysis of the unique phenotype of these cells suggests that they may represent the normal counterpart of the defective CD4-CD8 - T cells found in the lpr autoimmune mouse.
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