LAUSR

Significance Memory-like NK cells (NKG2C+CD57+FcεRIγ–) are established during CMV infection. Here, mass cytometry tracked the in vivo kinetics of CMV-induced memory NK cells generation and identified a unique subset of NKG2C+CD57+FcεRIγlow–dim as potentially prememory-like NK cells in CMV-infected kidney transplant patients. The study demonstrated that prememory-like NK cells with a high cytotoxic profile proliferate along with accumulation of new memory-like NK cells, whereas preexisting memory-like NK cells decreased in the peripheral blood after transplantation. Moreover, NKG2C+CD8+ T cells and cytotoxic γδ T cells also expand during CMV infection. This interplay of three different cytotoxic lymphocytes demonstrates a combinatorial immune response against CMV infection, which may contribute to preventing CMV-associated complication in organ transplantation. Cytomegalovirus (CMV) infection is associated with graft rejection in renal transplantation. Memory-like natural killer (NK) cells expressing NKG2C and lacking FcεRIγ are established during CMV infection. Additionally, CD8+ T cells expressing NKG2C have been observed in some CMV-seropositive patients. However, in vivo kinetics detailing the development and differentiation of these lymphocyte subsets during CMV infection remain limited. Here, we interrogated the in vivo kinetics of lymphocytes in CMV-infected renal transplant patients using longitudinal samples compared with those of nonviremic (NV) patients. Recipient CMV-seropositive (R+) patients had preexisting memory-like NK cells (NKG2C+CD57+FcεRIγ–) at baseline, which decreased in the periphery immediately after transplantation in both viremic and NV patients. We identified a subset of prememory-like NK cells (NKG2C+CD57+FcεRIγlow–dim) that increased during viremia in R+ viremic patients. These cells showed a higher cytotoxic profile than preexisting memory-like NK cells with transient up-regulation of FcεRIγ and Ki67 expression at the acute phase, with the subsequent accumulation of new memory-like NK cells at later phases of viremia. Furthermore, cytotoxic NKG2C+CD8+ T cells and γδ T cells significantly increased in viremic patients but not in NV patients. These three different cytotoxic cells combinatorially responded to viremia, showing a relatively early response in R+ viremic patients compared with recipient CMV-seronegative viremic patients. All viremic patients, except one, overcame viremia and did not experience graft rejection. These data provide insights into the in vivo dynamics and interplay of cytotoxic lymphocytes responding to CMV viremia, which are potentially linked with control of CMV viremia to prevent graft rejection.