Apoptosis resistance in peripheral blood lymphocytes of alopecia areata patients

Alopecia areata (AA) is a putative, cell-mediated autoimmune disease of anagen stage hair follicles. Inter- and intra-follicular lymphocytic infiltrates are associated with alopecia that may progress from an initially patchy presentation to extensive, even universal, hair loss. We previously noted in a mouse model of AA that regulatory T cells (Treg) are absent from draining lymph nodes and that expression of CD44v7 is transiently upregulated. Both features might explain autoreactive T cell persistence. Here we explored whether similar changes are seen in AA patients' peripheral blood mononuclear cells (PBMC). There was no clear evidence for a reduction in Treg as a possible means to support sustained T cell activation. However, progressive AA patients' PBMC displayed increased resistance towards apoptosis, which was accompanied by a decrease in CD95L+ and an increase in CD44v7+ cells. Notably, an expanded population of CD4+CD25+CD154+ T cells in progressive AA patients' PBMC was apoptosis resistant and expressed CD44v7. Thus, survival of activated T cells in progressive AA patients' PBMC is apparently sustained by downregulation of CD95L and upregulation of CD44v7 which is known to be associated with anti-apoptotic gene expression.