Phenotypic changes and proliferative activity of human gamma delta T cell receptor-bearing cells upon activation

We first compared the proliferative activity of alpha beta T cell receptor (TCR) (beta F1+) and gamma delta TCR (TCR delta-1+) human T cells after phytohaemagglutinin (PHA) stimulation by using double-colour immunofluorescence staining with Ki67 and anti-BrdU monoclonal antibodies (MoAbs). The dividing activity was higher within the alpha beta TCR cells: after 3 days of culture 69.9 +/- 5.9% of beta F1+ cells expressed Ki67, and 44.8 +/- 4.8% of these cells synthesized DNA as revealed by BrdU incorporation. In contrast, only 18.9 +/- 1.6% and 12.0 +/- 1.2% of TCR delta-1+ cells in the same samples were Ki67+ and BrdU+, respectively. Cells with V delta 1-J delta 1 usage (delta TCS-1+) showed a higher cycling activity than the rest of gamma delta TCR cells: after 3 days of PHA stimulation, 51.1 +/- 18.3% and 18.3 +/- 6.1% of such cells were in cycle and synthesized DNA, respectively. Next, we studied the expression of CD45 isoforms on peripheral blood alpha beta TCR and gamma delta TCR lymphocytes. Within the alpha beta TCR cells, two distinct subpopulations were distinguishable after labelling with SN130 (CD45RA) MoAb: 64.1 +/- 10.2% were bright, and 35.9 +/- 10.2% were dim or negative. Likewise, most TCR delta-1+ cells expressed SN130 (CD45RA): 87.5 +/- 3.0% were bright and 12.5 +/- 3.0% were dim. However, in contrast to alpha beta TCR+ cells, a high proportion (55.6 +/- 4.0%) of gamma delta TCR+ cells also expressed CD45RO molecules. Thus, most resting gamma delta TCR cells showed a pattern of CD45 isoform expression similar but not identical to that of 'memory' alpha beta TCR cells. Within the gamma delta TCR cell population the expression of CD45RO was heterogeneous because only 19.8 +/- 5.9% of cells bearing the V delta 1-J delta 1 form of the receptor (delta TCS-1+) were UCHL1 (CD45RO)+. Therefore, most gamma delta TCR cells with V delta 1-J delta 1 usage showed a CD45 isoform profile resembling that of 'naive' alpha beta TCR cells. These phenotypic features changed upon PHA stimulation: after 5 days of culture the proportion of TCR delta-1+ cells expressing UCHL1 increased to 86.0 +/- 3.1% and a two-fold increase in CD45RO expression was also observed in the delta TCS-1+ subpopulation.