TCR usage and functional capabilities of human γδ T cells at birth

Little is known about the γδ T cells in human neonatal umbilical cord blood. To compare neonatal cord blood and adult blood γδ T cells, we studied the Vγ and Vδ gene segment usage in these populations by flow cytometry, and we derived cord blood γδ T cell clones to determine their functional capabilities. Unlike adult blood γδ T cells that predominantly express Vγ2Vδ2 TCRs, neonatal cord blood γδ T cells expressed diverse Vγ and Vδ gene segments paired in a variety of combinations rarely observed in adults. γδ T cells clones derived from neonatal cord blood similarly expressed a diverse array of TCRs. These cord blood-derived γδ T cells clones had weak cytolytic activity when assayed for K562 tumor cell killing, lectin-mediated cytolysis, and redirected cytolysis. They also expressed lower levels of the CD2, LFA-1, and CD45RO cell surface receptors as compared with strongly cytolytic adult γδ T cell clones. These properties of the cord blood-derived γδ T cells clones, weak cytotoxic activity and low adhesion molecule expression, were similar to the properties of the CD4⁺ subset of adult γδ T cells. Thus, neonatal γδ T cells are functionally different from the majority of adult γδ T cells and display a distinct TCR repertoire and accessory molecule profile.