Human Vgamma9/Vdelta2 effector memory T cells express the killer cell lectin-like receptor G1 (KLRG1)

The killer cell lectin-like receptor G1 (KLRG1) is expressed in natural killer (NK) cells and effector memory alphabeta T cells. Gammadelta T cells represent an unconventional lymphocyte population that shares characteristics of NK cells and T cells and links innate and adaptive immunity. Vgamma9/Vdelta2 T cells comprise the majority of peripheral human gammadelta T cells and respond to the microbial metabolite (E)-4-hydroxy-3-methyl-but-2-enyl pyrophosphate (HMB-PP). Here, we demonstrate that KLRG1 is expressed in a significant proportion of Vgamma9/Vdelta2 T cells in cord blood and in the majority of peripheral Vgamma9/Vdelta2 T cells from adult donors. KLRG1+ Vgamma9/Vdelta2 T cells displayed an effector memory phenotype, as KLRG1 was expressed mainly in Vgamma9/Vdelta2 T cells lacking CD27, CD45RA, CD62L, and CC chemokine receptor 7 (CCR7). Unlike alphabeta T cells, where possession of KLRG1 identified effector memory cells with impaired proliferative capacity, KLRG1+ Vgamma9/Vdelta2 T cells were able to proliferate vigorously upon stimulation with HMB-PP in the presence of interleukin-2. Moreover, KLRG1 ligation on Vgamma9/Vdelta2 T cells by antibodies did not inhibit HMB-PP-induced proliferation and cytokine production nor cytolysis of Daudi cells.