CDw108 expression during T-cell development

We recently reported a gene encoding the human CDw108, a glycosylphosphatid ylinositol (GPI)-anchored membrane glycoprotein that: is preferentially exp ressed on activated T lymphocytes and erythrocytes. The present study inves tigated the expression of CDw108 on various tissues and cells, particularly on T cells during development. The murine CDw108 cDNA was cloned initially and it was highly homologous to the human CDw108 (88.0% or 89.3% similarit y at the nucleotide or amino acid level, respectively) or identical to the murine semaphorin K1/Sema7A. The CDw108 mRNA was demonstrated in a few tiss ues including thymus and brain with the highest expression coming on day 7 in whole embryo followed by relatively consistent expression during develop ment. Cell-surface expression of the CDw108 during T-cell development was f urther examined by flow cytometry in the human umbilical cord blood and thy mus. It was preferentially expressed on a CD34(+) stem cell population of u mbilical cord blood, and CD3(dull) CD34(+/-). CD117 (c-kit)(+) CD4(bright) CD8(bright) cells in the thymus that are involved in the stage of positive selection. These results suggest the contribution of CDw108 in T-cell devel opment, especially in the stage of positive selection in the thymus.