Functional characteristics of human peripheral blood alpha/betaTCR+, CD4- and CD8- double-negative (DN) T cells.

The function of human peripheral blood alpha/betaTCR positive, CD4- and CD8- double-negative T lymphocytes (DN cells) in vivo is not completely understood. The response of immunomagnetically isolated DN cells to PHA and anti-CD3 was compared to the response of single-positive (SP) CD4 and CD8 subsets. Proliferation of DN cells in response to PHA was largely independent of APC. This suggests activation requirements for DN cells that are different from SP cells. Upon activation, HLA-DR was found to be upregulated early on DN cells, and IL-4 and IL-10 were detected in the supernatants of DN cells. These observations in vitro could correspond with an immunoregulatory role of human DN cells in vivo.