Change in perforin-positive peripheral blood lymphocyte (PBL) subpopulations following exercise

Perforin, one of the cytotoxic proteins of the immune system, plays a promi nent role in protection against viral and bacterial infections. We investig ated its expression in PBL and their CD3(+), CD4(+), CD8(+) and CD16(+) and /or CD56(+) subpopulations in endurance athletes before and after a triathl on. Lymphocyte subpopulations were analysed by flow cytometry following sep aration of peripheral blood mononuclear cells and staining with antibodies against specific membrane antigens and intracellular perforin. The number o f total lymphocytes decreased from 2.1 x 10(3)/mu l before the triathlon to 1.0 x 10(3)/mu l Ih after the triathlon (P < 0.01). Interestingly, there w as already a significant spontaneous decline in the percentage of CD3(+)/pe rforin(+), and in CD8(+)/perforin(+) cells, in the week proceeding the tria thlon, when subjects were instructed to refrain from strenuous exercise tra ining. The percentage of CD3+/perforin+, CD8+/perforin+ and CD16+ and/or CD 56(+)/perforin(+) cells in each lymphocyte subpopulation decreased 1 h afte r exercise even further from 14.3% to 5.8% (P < 0.05), 18.5% 6.5% (P < 0.05 ) and 77.3% to 67.3%, respectively. However, at 18 h and 48 h after exercis e the percentage of perforin-expressing CD3(+), CD8(+) and CD16(+)/56(+) ce lls increased again towards baseline levels. Compared with normal controls, baseline perforin co-expression in CD3(+) and CD8(+) lymphocytes was signi ficantly higher in trained athletes. From our data we conclude that trained athletes have an increased percentage of perforin(+) PBL and that followin g exercise the percentage of perforin(+) and therefore potentially cytotoxi c lymphocytes transiently decreases in peripheral blood.