EXPRESSION OF CD45 ISOFORMS BY FRESH AND ACTIVATED HUMAN GAMMA-DELTA-T LYMPHOCYTES AND NATURAL-KILLER-CELLS

Naive and primed alpha-beta-T cells can be distinguished on the basis of their differential expression of CD45RA and CD45RO, respectively. The present study indicates that these CD45-isoforms also identify naive and primed maturational stages of gamma-delta-T cells and natural killer (NK) cells. In peripheral blood, all V-gamma-9-V-delta-2 gamma-delta-T cells reportedly express CD45RO whereas all V-delta gamma-delta T cells lack CD45RO. Here, we show that these CD45RO- V-delta gamma-delta-T cells all express CD45RA and the CD45RO+ V-gamma-9-V-delta-2 gamma-delta-cells lack expression of CD45RA. The V-delta-T cells acquired CD45RO expression and lost part of their surface CD45RA, following in vitro activation with phytohaemagglutinin or IL-2. Also the CD3-CD16+ NK cells in peripheral blood that are uniformly CD45RA+CD45RO- completely converted to the CD45RA-CD45RO+ phenotype upon in vitro activation. Moreover, all cloned V-gamma-9-V-delta-2 and V-delta-1 T cells and NK cells express CD45RO and lack expression of CD45RA. Our results strongly suggest that CD45RA and CD45RO are genuine markers for naive and primed lymphocytes that represent distinct differentiation lineages.