Flow cytometric detection of perforin in normal human lymphocyte subpopulations defined by expression of activation/differentiation antigens

We investigated with three-color how cytometry the expression of perforin (Pf) in normal human lymphocyte subpopulations identified by means of activation and differentiation-related antigens. Interestingly, Pf could be detected in a substantial subset (13 +/- 2%) of memory CD4(+)CD45RO(+) cells, on relevant percentages of memory (CD45RO(+)) and naive (CD45RA(+)) CD8(+) cells and on virtually all CD3(-)CD16(+), CD3(-)CD56(+) and NKBl(+) natural killer cells, as expected. The analysis of fluorescence intensity showed higher levels of Pf expression on CD8(dim) and NK cells compared to CD8(bright) and CD4(+) lymphocytes, Pf and CD69, HLA-DR, CD95 and CD25 activation/differentiation-related antigens were never co-expressed. On average, 15 +/- 3% of CD3(+)CD28(+) cells were found to be Pf(+), in line with a previously activated or memory cell type. Comparable percentages of CD8(+)CDllb(-) (cytotoxic) and CD8(+)CDllb(+) (suppressor)T cells were Pf(+). Multiparameter flow cytometry is a powerful tool to detect minute fractions of Pf-expressing cells in heterogeneous populations. (C) 1998 Elsevier Science B.V.