Human lymphocytes bearing T cell receptor gamma/delta are phenotypically diverse and evenly distributed throughout the lymphoid system.

Abstract

A direct quantitative and phenotypic cytofluorographic analysis of TCR-.gamma./.delta.+ lymphocytes as well as an immunohistologic study of their tissue distribution and microanatomy was made possible by the availability of two mAbs (anti-TCR-.delta.1 and anti-C.gamma.M1) specific for framework determinants on human TCR .gamma. and .delta. chains, respectively. TCR-.gamma./.delta.+ lymphocytes, ranging between > 0.5 and 16% of CD3+ cells, were found in fetal and postnatal thymus, fetal and adult peripheral lymphoid organs, and adult peripheral blood. While TCR-.gamma./.delta.+ lymphocytes comprised a small subpopulation of T cells (mean, .apprx. 4%) occasionally > 10-16% of CD3+ cells expressed TCR-.gamma./.delta.. Virtually all TCR-.gamma./.delta.+ thymocytes/lymphocytes expressed CD7, CD2, and CD5 but were heterogeneous with respect to their expression of CD1, CD4, CD8, CD28, CD11b, CD16, and Leu-7. Human TCR-.gamma./.delta.+ cells populate both organized lymphoid tissues (thymus, tonsil, lymphnode, and spleen) as well as the gut- and skin-associated lymphoid systems at similar frequencies without obvious tropism for epithelial microenvironments. TCR-.gamma./.delta.+ lymphocytes tend to be located within a given organ wherever TCR-.alpha./.beta.+ lymphocytes are found. This study shows that TCR-.gamma./.delta.+ lymphocytes constitute a small but numerically important, phenotypically diverse T cell population distributed throughout the body. These results support the concept that TCR-.gamma./.delta.+ cells comprise a distinct, functionally heterogeneous, mature T cell sublineage that may substantially broaden the T cell repertoire at all immunologically relevant sites.