Acute graft-versus-host disease (aGVHD) is associated with high risk of morbidity and mortality and is a common complication after double umbilical cord blood (UCB) transplantation. To reduce these risks, we established a method of CD4 ؉ CD25 ؉ FoxP3 ؉ T regulatory cell (Treg) enrichment from cryopreserved UCB followed by a 18 ؉ 1-day expansion culture including anti-CD3/anti-CD28 antibody-coated beads and recombinant human interleukin-2. In a "first-in-human"

During mouse cytomegalovirus (CMV) infection, a population of Ly49H ؉ natural killer (NK) cells expands and is responsible for disease clearance through the induction of a "memory NK-cell response." Whether similar events occur in human CMV infection is unknown. In the present study, we characterized the kinetics of the NK-cell response to CMV reactivation in human recipients after hematopoietic cell transplantation. During acute infection, NKG2C ؉ NK cells expanded and were potent producers of IFN␥. NKG2C ؉ NK cells predominately expressed killer cell immunoglobulin-like receptor, and self-killer cell immunoglobulinlike receptors were required for robust IFN␥ production. During the first year after transplantation, CMV reactivation induced a more mature phenotype characterized by an increase in CD56 dim NK cells. Strikingly, increased frequencies of NKG2C ؉ NK cells persisted and continued to increase in recipients who reactivated CMV, whereas these cells remained at low frequency in recipients without CMV reactivation. Persisting NKG2C ؉ NK cells lacked NKG2A, expressed CD158b, preferentially acquired CD57, and were potent producers of IFN␥ during the first year after transplantation. Recipients who reactivated CMV also expressed higher amounts of IFN␥, T-bet, and IL-15R␣ mRNA transcripts. Our findings support the emerging concept that CMV-induced innate memory-cell populations may contribute to malignant disease relapse protection and infectious disease control long after transplantation. (Blood. 2012; 119(11):2665-2674) IntroductionNatural killer (NK) cells are important effectors during the host innate immune response to viral infections. They can recognize and eliminate virally infected cells, interact with dendritic cells, and produce a range of cytokines and chemokines (eg, IFN␥, TNF-␣, MIP-1␣, MIP-1␤, and RANTES) that recruit and modulate the adaptive immune response.Under normal homeostatic conditions, a balance of activating and inhibitory signals tightly controls NK-cell function. 1,2 The best-characterized inhibitory receptors are the inhibitory killer cell immunoglobulin-like receptors (KIRs) that recognize allelic epitopes present on certain class I human leukocyte antigens (HLAs) and the C-type lectin-like receptor NKG2A, which recognizes the nonclassic class I HLA, HLA-E. 3,4 Activating signals are mediated by receptor families, including activating KIR, NKG2C, NKG2D, the natural cytotoxicity receptors (NKp30, NKp44, and NKp46), CD16, and CD244. 1 When self HLA is down-regulated, cells are susceptible to NK-cell lysis because of the lack of ligands for the inhibitory receptors, a phenomenon known as the "missing self" hypothesis. 5,6 Human cytomegalovirus (CMV), a member of the Herpesviridae family, causes asymptomatic or mild illness in healthy people. 7 CMV remains latent in infected hosts and, by adulthood, approximately 60% of people in the United States are seropositive for CMV. 8 However, for patients immunosuppressed due to HIV infection or solid organ or hematopoietic call transplantatio...

In this study, we show that IFN-αβ can have a direct role in linking innate and adaptive responses by providing the “third signal” needed by naive CD8 T cells responding to Ag and costimulatory ligands. Stimulation of CD8 T cells in the absence of a third signal leads to proliferation, but clonal expansion is limited by poor survival and effector functions do not develop. We show that IFN-αβ can provide the third signal directly to CD8 T cells via a STAT4-dependent pathway to stimulate survival, development of cytolytic function, and production of IFN-γ. Provision of the third signal by either IFN-αβ or IL-12 results in regulation of the expression of a number of genes, including several that encode proteins critical for effector function.

Stimulation of naïve CD8+ T cells with antigen and costimulation results in proliferation and weak clonal expansion, but the cells fail to develop effector functions and are tolerant long term. Initiation of the program leading to the strong expansion and development of effector functions and memory requires a third signal that can be provided by interleukin-12 (IL-12) or interferon-alpha (IFN-alpha). CD4+ T cells condition dendritic cells (DCs) to effectively present antigen to CD8+ T cells, and this conditioning involves, at least in part, CD40-dependent upregulation of the production of these signal 3 cytokines by the DCs. Upon being fully activated, the cytotoxic T lymphocytes develop activation-induced non-responsiveness (AINR), a form of split anergy characterized by an inability to produce IL-2 to support continued expansion. If antigen remains present, IL-2 provided by CD4+ T cells can reverse AINR to allow further expansion of the effector population and conversion to responsive memory cells following antigen clearance. If IL-2 or potentially other proliferative signals are not available, persistent antigen holds cells in the AINR state and prevents the development of a responsive memory population. Thus, in addition to antigen and costimulation, CD8+ T cells require cytokine signals at distinct stages of the response to be programmed for optimal generation of effector and memory populations.