Killer cell lectin-like receptor G1 (KLRG1) is one of several inhibitory killer cell lectin-like receptors expressed by NK cells and T lymphocytes, mainly CD8+ effector/memory cells that can secrete cytokines but have poor proliferative capacity. Using multiparameter flow cytometry, we studied KLRG1 expression on CD8+ T cells specific for epitopes of CMV, EBV, influenza, and HIV. Over 92% of CD8+ cells specific for CMV or EBV expressed KLRG1 during the latent stage of these chronic infections. CD8+ T cell cells specific for HIV epitopes were mostly (72–89%) KLRG1+, even though not quite at the level of predominance noted with CMV or EBV. Lower frequency of KLRG1 expression was observed among CD8+ cells specific for influenza (40–73%), a resolved infection without a latent stage. We further observed that CD8+ cells expressing CD57, a marker of replicative senescence, also expressed KLRG1; however, a population of CD57−KLRG1+ cells was also identified. This population may represent a “memory” phenotype, because they also expressed CD27, CD28, CCR7, and CD127. In contrast, CD57+KLRG1+ cells did not express CD27, CD28, and CCR7, and expressed CD127 at a much lower frequency, indicating that they represent effector cells that are truly terminally differentiated. The combination of KLRG1 and CD57 expression might thus aid in refining functional characterization of CD8+ T cell subsets.

A B S T R A C T PurposeTo characterize relationships between specific immune cell subsets in bone marrow (BM) or granulocyte colony-stimulating factor-mobilized peripheral blood (PB) stem cells collected from unrelated donors and clinical outcomes of patients undergoing transplantation in BMTCTN 0201. Patients and MethodsFresh aliquots of 161 BM and 147 PB stem-cell allografts from North American donors randomly assigned to donate BM or PB stem cells and numbers of transplanted cells were correlated with overall survival (OS), relapse, and graft-versus-host disease (GvHD). ResultsPatients with evaluable grafts were similar to all BMTCTN 0201 patients. The numbers of plasmacytoid dendritic cells (pDCs) and naïve T cells (Tns) in BM allografts were independently associated with OS in multivariable analyses including recipient and donor characteristics, such as human leukocyte antigen mismatch, age, and use of antithymocyte globulin. BM recipients of Ͼ median number of pDCs, naïve CD8 ϩ T cells (CD8Tns), or naïve CD4 ϩ T cells (CD4Tns) had better 3-year OS (pDCs, 56% v 35%; P ϭ .025; CD8Tns, 56% v 37%; P ϭ .012; CD4Tns, 55% v 37%; P ϭ .009). Transplantation of more BM Tns was associated with less grade 3 to 4 acute GvHD but similar rates of relapse. Transplantation of more BM pDCs was associated with fewer deaths resulting from GvHD or from graft rejection. Analysis of PB grafts did not identify a donor cell subset significantly associated with OS, relapse, or GvHD. ConclusionDonor immune cells in BM but not PB stem-cell grafts were associated with survival after unrelated-donor allogeneic hematopoietic stem-cell transplantation. The biologic activity of donor immune cells in allogeneic transplantation varied between graft sources. Donor grafts with more BM-derived Tns and pDCs favorably regulated post-transplantation immunity in allogeneic hematopoietic stem-cell transplantation. J Clin Oncol 32:2365-2372. © 2014 by American Society of Clinical Oncology INTRODUCTIONMuch of the clinical utility of allogeneic hematopoietic stem-cell transplantation (alloHSCT) in treating patients with hematologic malignancies depends on the graft-versus-leukemia (GvL) activity of donor T cells.1-3 Improving outcomes after alloHSCT requires understanding how the GvL or graft-versushost disease (GvHD) functions of donor T cells are regulated, including interactions with donor or host dendritic cells (DCs) and homing to hematolymphoid or GvHD-target organs. 1,4 Previous reports have suggested the content of donor DCs is associated with incidence of chronic GvHD and relapse, 5 and the content of CD34 ϩ cells is associated with survival 6 and GvHD among peripheral blood (PB) stem-cell allograft recipients. 7 To explore associations between cell subsets in the allograft with clinical outcomes in a prospective clinical trial, fresh aliquots of bone marrow (BM) and PB stem-cell grafts collected from unrelated volunteer donors recruited in BMTCTN (Blood and Marrow Transplant Clinical Trials Network) 0201 were analyzed for their cont...

Flow cytometry has evolved over the past 30 y from a niche laboratory technique to a routine tool used by clinical pathologists and immunologists for diagnosis and monitoring of patients with cancer and immune deficiencies. Identification of novel patterns of expressed Ags has led to the recognition of cancers with unique pathophysiologies and treatment strategies. FACS had permitted the isolation of tumor-free populations of hematopoietic stem cells for cancer patients undergoing stem cell transplantation. Adaptation of flow cytometry to the analysis of multiplex arrays of fluorescent beads that selectively capture proteins and specific DNA sequences has produced highly sensitive and rapid methods for high through-put analysis of cytokines, Abs, and HLA genotypes. Automated data analysis has contributed to the development of a “cytomics” field that integrates cellular physiology, genomics, and proteomics. In this article, we review the impact of the flow cytometer in these areas of medical practice.