TCRαβ repertoire diversity of human naturally occurring CD4+CD25+ regulatory T cells

We examined the up T cell receptor (TCR) repertoire of naturally Occurring CD4+CD25+ regulatory T (Treg) cells isolated from healthy human blood. Three-color FACS analysis demonstrated that the usage of variable region segments of TCR beta chains by CD4+CD25+ cells did not differ from those of CD4+CD25- cells. Complementarity-determining region 3 (CDR3) size distribution analyses demonstrated that the repertoire diversity of CDR3 beta was almost identical between CD4+CD25+ and CD4+CD25- T cell subsets, and that there was no skewing of the CDR3 beta repertoire of CD4+CD25+ T cells. In contrast, in vitro activated CD4+CD25+ T cells by cytomegalovirus-derived antigens showed a skewed CDR3 size distribution pattern. These findings support the hypothesis that naturally Occurring CD4+CD25+ T cell subset in humans is largely composed of a T cell lineage positively selected in the thymus as a consequence of the interaction between self-peptides and TCRs and not derived from recent activation by a limited array of antigens. (c) 2005 Elsevier B.V. All rights reserved.