Expression of granzyme B during primary cytomegalovirus infection after renal transplantation

CD8(+) T cells employ granzyme B (GrB) to induce apoptosis in target cells. Increased expression of GrB has been put forward as a diagnostic marker in transplant rejection and viral infection. Three-color dow cytometric analy sis revealed that peripheral blood CD8(+) T lymphocytosis during primary cy tomegalovirus infection after renal transplantation resulted from expansion of a CD8(+)GrB(+)CD62L(+) T cell subset that was almost absent during stab le transplant function or acute rejection. This expansion coincided with a temporary increase in systemic soluble GrB (sGrB) levels. No such increase was observed during stable transplant function or acute rejection. Thus, th e primary immune response to cytomegalovirus infection is accompanied by ap pearance of CD8(+)GrB(+)CD62L(+) T cells and increased sGrB levels in the p eripheral blood compartment. Determination of the latter may provide a nove l approach for monitoring viral infections.