Impact of age, gender, and race on circulating γδ T cells.

A major subset of human peripheral blood γδ T cells expresses the Vγ2Vδ2 T cell receptor and responds to malignant or infectious diseases. We noted significant differences in the numbers of Vγ2Vδ2 T cells in blood samples from healthy Caucasian CA or African American (AA) donors. On average, CA donors had 3.71% ± 4.37% Vδ2 cells (as a percentage of total lymphocytes) compared with 1.18% ± 2.14% Vδ2 cells for AA donors (p < 0.0001). Age and race had the greatest impact on Vδ2 cell levels; the effect of age was similar for both racial groups. The Vδ2 cell population was dominated, for both donor groups, by cells expressing the Vγ2-Jγ1.2 Vδ2 T cell receptor, an apparent result of strong positive selection and there was substantial overlap in the public Vγ2 clonotypes from both racial groups. Mechanisms for selection and amplification of Vδ2 cells are nearly identical for both groups, despite the significant difference in baseline levels. These data show that appropriate controls, matched for age and race, may be required for clinical studies of Vγ2Vδ2 T cells in infectious disease or cancer and raise important questions about the mechanisms regulating the levels of circulating Vδ2 cells.