Coordinated expansion of both memory T cells and NK cells in response to CMV infection in humans

NK cells are key players in the fight against persistent viruses. Human cytomegalovirus (HCMV) infection is associated with the presence of a population of CD16⁺ CD56^dim NKG2C⁺ NK cells in both acutely and latently infected individuals. Here, we studied the nature of these terminally differentiated NK cells in different human populations infected with HCMV: healthy donors stratified by age, thymectomized individuals, pregnant women suffering from primary CMV infection, and lung transplant patients. Both CD16⁺ CD56^dim NK‐ and CD8 T‐cell phenotypes as well as functional capacities were determined and stratified according to age and/or CMV event. Similarly to T‐cell responsiveness, we observe an accumulation over time of NKG2C⁺ NK cells, which preferentially expressed CD57. This accumulation is particularly prominent in elderly and amplified further by CMV infection. Latent HCMV infection (without replication) is sufficient for NKG2C⁺ CD57⁺ NK cells to persist in healthy individuals but is not necessarily required in old age. Collectively, the present work supports the emerging concept that CMV shapes both innate and adaptive immunity in humans.     

CMV drives the expansion of highly functional memory T cells expressing NK‐cell receptors in renal transplant recipients

Cytomegalovirus (CMV) is a common opportunistic infection encountered in renal transplant recipients (RTRs) and may be reactivated without symptoms at any time post‐transplant. We describe how active and latent CMV affect T‐cell subsets in RTRs who are stable on maintenance therapy. T‐cell responses to CMV were assessed in RTRs (n = 54) >2 years post‐transplant, and healthy controls (n = 38). Seven RTRs had CMV DNA detectable in plasma. CMV antibody and DNA aligned with increased proportions of CD8⁺ T cells and reduced CD4/CD8 ratios. This paralleled an expansion of effector memory T‐cell (T_EM), terminally differentiated T‐cell (T_EMRA) and CD57⁺ T_EMRA cell populations. Expression of NK‐cell receptors, LIR‐1 and KLRG1 on CD4⁺ and CD8⁺ CD57⁺ T_EM and T_EMRA cells correlated with elevated interferon‐γ and cytotoxic responses to anti‐CD3 and increased cytotoxic responses to CMV phosphoprotein (pp) 65 in RTRs who carried CMV DNA. CD8⁺ T cells from all CMV seropositive RTRs responded efficiently to CMV immediate early (IE) ‐1 peptides. The data show that latent and active CMV infection can alter T‐cell subsets in RTRs many years after transplantation, and up‐regulate T‐cell expression of NK‐cell receptors. This may enhance effector responses of CD4⁺ and CD8⁺ T cells against CMV.     

Adaptive reconfiguration of the human NK‐cell compartment in response to cytomegalovirus: A different perspective of the host‐pathogen interaction

As discussed in this review, human cytomegalovirus (HCMV) infection in healthy individuals is associated with a variable and persistent increase of NK cells expressing the CD94/NKG2C activating receptor. The expansion of NKG2C⁺ NK cells reported in other infectious diseases is systematically associated with HCMV co‐infection. The functionally mature NKG2C^bright NK‐cell subset expanding in HCMV⁺ individuals displays inhibitory Ig‐like receptors (KIR and LILRB1) specific for self HLA class I, and low levels of NKp46 and NKp30 activating receptors. Such reconfiguration of the NK‐cell compartment appears particularly marked in immunocompromised patients and in children with symptomatic congenital infection, thus suggesting that its magnitude may be inversely related with the efficiency of the T‐cell‐mediated response. This effect of HCMV infection is reminiscent of the pattern of response of murine Ly49H⁺ NK cells against murine CMV (MCMV), and it has been hypothesized that a cognate interaction of the CD94/NKG2C receptor with HCMV‐infected cells may drive the expansion of the corresponding NK‐cell subset. Yet, the precise role of NKG2C⁺ cells in the control of HCMV infection, the molecular mechanisms underlying the NK‐cell compartment redistribution, as well as its putative influence in the response to other pathogens and tumors remain open issues.     

Absence of cytotoxic molecules in CD8- and/or CD56-positive adult T-cell leukaemia/lymphoma

Adult T-cell leukaemia/lymphoma (ATLL) cells usually exhibit a CD4⁺ (helper/inducer) phenotype (CD4⁺/8^–/56^–), and only a minority of tumours express the CD8 (cytotoxic/suppressor) or CD56 (natural killer [NK]-associated) antigens. TIA-1 is a cytotoxic granule-associated protein expressed in NK cells and cytotoxic T lymphocytes (CTLs). Granzyme B, perforin and Fas ligand (FasL) are also expressed in activated CTLs and NK cells. To clarify the cytotoxic potential of ATLL cells, immunohistochemistry was performed in CD8⁺ and/or CD56⁺ ATLL cells, using anti-TIA-1, anti-granzyme B, anti-perforin and anti-FasL antibodies. We studied nine cases of CD8⁺ and/or CD56+ ATLL, all of which exhibited monoclonal integration of human T-cell leukaemia virus type 1 (HTLV-1) proviral DNA. Four cases exhibited a CD8⁺/CD56^– phenotype, four others had a CD8^–/CD56⁺ phenotype, and one was CD8⁺/CD56⁺. All but one case also expressed the surface antigens CD3, TCR αβ, and CD4. Expression of granzyme B and TIA-1 were demonstrated in three and two cases, respectively, but none expressed perforin or FasL. In the control study, 10 cases with typical CD3⁺/4⁺/8^–/56^– ATLL demonstrated no expression of those cytotoxic-associated proteins. Our findings suggest that CD8 and/or CD56 positivity probably confer(s) no cytotoxic function on ATLL cells, and it is possible that CD8 and CD56 may be simply aberrant surface markers in ATLL. Received: 20 January 1999 / Accepted: 13 April 1999     

CD2–CD58 interactions are pivotal for the activation and function of adaptive natural killer cells in human cytomegalovirus infection

The existence and expansion of adaptive NK‐cell subsets have been linked to HCMV infection. Phenotypically, a majority of adaptive NK cells expresses the activating receptor NKG2C and CD57. Some of the molecular factors driving the expansion of NKG2C⁺CD57⁺ NK cells in HCMV infection have been identified. The direct interaction of adaptive NK cells with HCMV‐infected cells, preceding the expansion, however, remains less studied. Recently, adaptive NK cells were reported to express higher levels of the co‐activating receptor CD2. We explored whether CD2 was directly involved in the response of adaptive NK cells to HCMV. In a co‐culture system of human PBMCs and productively infected fibroblasts, we observed an upregulation of CD69, CD25, and HLA‐DR on all NK cells. However, only in adaptive NK cells was this increase largely blocked by antibodies against CD2 and CD58. Functionally, this blockade also resulted in diminished production of IFN‐γ and TNF‐α by adaptive human NK cells in response to HCMV‐infected cells. Our results demonstrate that binding of CD2 to upregulated CD58 on infected cells is a critical event for antibody‐mediated activation and subsequent effector functions of adaptive NKG2C⁺CD57⁺ NK cells during the antiviral response.     

Early Cytomegalovirus Reactivation and Expansion of CD56brightCD16dim/−DNAM1+ Natural Killer Cells Are Associated with Antileukemia Effect after Haploidentical Stem Cell Transplantation in Acute Leukemia

Cytomegalovirus (CMV) infection is a major complication after allogeneic hematopoietic stem cell transplantation but is suggested to exert a strong antileukemia effect in part due to alterations in the composition of natural killer (NK) cells. We evaluated the impact of early CMV reactivation and changes in NK cell subset recovery on relapse rate and survival after haploidentical stem cell transplantation (haploSCT) for acute leukemia. Fifty patients with acute leukemia who received haploSCT were analyzed. Expression of T cells and specific receptors (NKG2A, NKG2D, DNAM1, and CD57) on circulating NK cells (CD56^brightCD16^dim/– or CD56^dimCD16⁺ cells) was serially measured using multiparametric flow cytometry. CMV reactivation during the first 100 days was observed in 41 patients (82%) at a median of 23 days after haploSCT. The incidence of acute graft-versus-host disease (GVHD) and chronic GVHD tended to be higher in patients with CMV reactivation, although this difference was not statistically significant. Multivariate analysis showed that CMV reactivation (P = .011) and a dose of infused T cells > 3.2 × 10⁸/kg (P = .027) were independent predictors of a reduced relapse risk and only CMV reactivation (P = .029) was an independent predictor of improved leukemia-free survival. CD56^brightCD16^dim/?DNAM1⁺NK cell counts increased from day 30 to 90 in patients with CMV reactivation but decreased after day 30 in patients without CMV reactivation. An increase in CD56^brightCD16^dim/?DNAM1⁺ NK cells was not associated with the occurrence of chronic GVHD but was associated with a reduced cumulative relapse rate (16.4% versus 58.0%, P = .019). Multivariate analysis indicates that an increase in the CD56^brightCD16^dim/?DNAM1⁺NK cell count was an independent predictor of reduced relapse risk. Our study demonstrates a significant correlation between low relapse rates and CMV reactivation as well as the recovery of CD56^brightCD16^dim/?DNAM1⁺ NK cells, providing valuable information for understanding the plausible immunologic mechanism of the graft-versus-leukemia effect.     

Influence of congenital human cytomegalovirus infection and the NKG2C genotype on NK‐cell subset distribution in children

Human cytomegalovirus (HCMV) has been reported to reshape the NK‐cell receptor (NKR) distribution, promoting an expansion of CD94/NKG2C⁺ NK and T cells. The role of NK cells in congenital HCMV infection is ill‐defined. Here we studied the expression of NKR (i.e., NKG2C, NKG2A, LILRB1, CD161) and the frequency of the NKG2C gene deletion in children with past congenital infection, both symptomatic (n = 15) and asymptomatic (n = 11), including as controls children with postnatal infection (n = 11) and noninfected (n = 20). The expansion of NKG2C⁺ NK cells in HCMV‐infected individuals appeared particularly marked and was associated with an increased number of LILRB1⁺ NK cells in cases with symptomatic congenital infection. Increased numbers of NKG2C⁺, NKG2A⁺, and CD161⁺ T cells were also associated to HCMV infection. The NKG2C deletion frequency was comparable in children with congenital HCMV infection and controls. Remarkably, the homozygous NKG2C^+/+ genotype appeared associated with increased absolute numbers of NKG2C⁺ NK cells. Moreover, HCMV‐infected NKG2C^+/+ children displayed higher absolute numbers of NKG2A⁺ and total NK cells than NKG2C^+/? individuals. Our study provides novel insights on the impact of HCMV infection on the homeostasis of the NK‐cell compartment in children, revealing a modulatory influence of NKG2C copy number.     

Immunological features of sporadic multinodular goiter

Summary The origin of sporadic multinodular goiter is still uncertain. To obtain information on a number of unexplored immunological features, the distribution and characterization of T, B, and natural killer lymphocyte subsets were studied in the peripheral blood of 15 patients with multinodular goiter; 8 patients with Graves' disease (for reference purposes with a well-characterized autoimmune disease) and 29 age- and sex-matched healthy controls, combining double-staining immunofluorescence technique with monoclonal antibodies and flow cytometry. Although in both thyroid diseases increased CD3⁺ HLA-DR⁺ activated T cells (P < 0.01) were detected, in Graves' disease this was associated with decreased numbers of CD8⁺ cells (P<0.05) and an increased CD4/CD8 ratio (P < 0.01). These abnormalities were absent in multinodular goiter, which displayed increased CD8⁺ CD57⁺ cytotoxic/suppressor cells (P < 0.01). There was an increase in the percentage of natural killer cells expressing CD16 and CD57 antigens in multinodular goiter but not in Graves' disease. The B-cell associated antigens CD 19 and CD19⁺ CD5⁺ were significantly increased in Graves' disease (P < 0.01), while the multinodular goiter patients exhibited only an increased number of B cells coexpressing the CD5 antigen (CD19⁺ CD5⁺), which was unrelated to the titers of antimicrosomal and antithyroglobulin autoantibodies. Our results point to the presence of several abnormalities of peripheral T, B, and natural killer lymphocytes in sporadic multinodular goiter, with a distribution pattern quite different from that observed in Graves' disease. These results support the notion that, in contrast to Graves' disease, in sporadic multinodular goiter different suppressor and/or cytotoxic mechanisms are set up by the immune system, reflecting either pathogenic mechanisms of the disease or an immune response to pathological growing tissue.Abbreviations FITC fluorescein isothiocyanate - NK natural killer - PE phycoerythrin - T₃ triiodothyronine - T₄ thyroxine - TBII thyroid binding inhibitory immunoglobulin - TSH thyroid-stimulating hormone     

Increased expressions of NKp44, NKp46 on NK/NKT-like cells are associated with impaired cytolytic function in self-limiting hepatitis E infection

We have characterized the NK/NKT-like cells in patients with self-limiting hepatitis E infection. The distribution of peripheral NK/NKT-like cells, expressions of activation receptors, cytotoxic potential and effector function of NK/NKT-like cells from fresh peripheral blood mononuclear cells of 86 acute patients, 101 recovered and 54 control individuals were assessed. Activated NKT-like (CD16⁺ CD56⁺ CD3⁺) cells were high in the patient groups. On CD56⁺ CD3^? cells, NKp44 and NKp46 expressions were high in the acute patients, whereas NKp30, NKp44, NKp46 and NKG2D were high in the recovered individuals. On CD56⁺ CD3⁺ cells, NKp44, NKp46 and NKG2D expressions were high in the recovered but NKp30 was low in both the patient groups. Collectively, the current study elucidates the role of NK/NKT-like cells demonstrating phenotypic alterations of activated NKT-like cells and activation receptors, lack of CD107a expression and functional impairment of peripheral NK/NKT-like cells in self-limiting hepatitis E infection.     

The specific NK cell response in concert with perforin prevents CD8<Superscript>+</Superscript> T cell-mediated immunopathology after mouse cytomegalovirus infection

Natural killer (NK) and CD8⁺ T cells play a crucial role in the control of mouse cytomegalovirus (MCMV) infection. These effector cells exert their functions by releasing antiviral cytokines and by cytolytic mechanisms including perforin activation. In addition to their role in virus control, NK cells play an immunoregulatory role since they shape the CD8⁺ T cell response to MCMV. To investigate the role of perforin-dependent cytolytic mechanism in NK cell modulation of CD8⁺ T cell response during acute MCMV infection, we have used perforin-deficient C57BL/6 mice (Prf1^?/?) and have shown that virus control by CD8⁺ T cells in Prf1^?/? mice is more efficient if NK cells are activated by the engagement of the Ly49H receptor with the m157 MCMV protein. A lack of perforin results in severe liver inflammation after MCMV infection, which is characterized by immunopathological lesions that are more pronounced in Prf1^?/? mice infected with virus unable to activate NK cells. This immunopathology is caused by an abundant infiltration of activated CD8⁺ T cells. The depletion of CD8⁺ T cells has markedly reduced pathohistological lesions in the liver and improved the survival of Prf1^?/? mice in spite of an increased viral load. Altogether, the results of our study suggest that a lack of perforin and absence of the specific activation of NK cells during acute MCMV infection lead to an unleashed CD8⁺ T cell response that is detrimental for the host.     

Compartmentalized cytotoxic immune response leads to distinct pathogenic roles of natural killer and senescent CD8+ T cells in human cutaneous leishmaniasis

Cytotoxic activity mediated by CD8⁺ T cells is the main signature of the immunopathogenesis of cutaneous leishmaniasis (CL). Here, we performed a broad evaluation of natural killer (NK) cell phenotypic and functional features during cutaneous leishmaniasis. We demonstrate for the first time that CL patients present the accumulation of circulating NK cells with multiple features of replicative senescence including low proliferative capacity and shorter telomeres, elevated expression of CD57, KLRG1 but diminished CD27 stimulatory receptor expression. Moreover, they exhibited higher cytotoxic and inflammatory potential than age-matched controls. The accumulation of circulating senescent NK cells (CD56^dim CD57^bright) correlated positively with skin lesion size in the same patients, suggesting that they, like circulating senescent CD8⁺ T cells, may contribute to the immunopathology of CL. However, this senescent population had lower cutaneous lymphocyte antigen expression and so had diminished skin-homing potential compared with total or senescent CD8⁺ T cells. This was confirmed in CL skin lesions where we found a predominance of CD8⁺ T cells (both senescent and non-senescent) that correlated with the severity of the disease. Although there was also a correlation between the proportions of senescent NK cells (CD56⁺ CD57⁺) in the skin and lesion size, this was less evident. Collectively our results demonstrate first-hand that senescent cytotoxic cells may mediate skin pathology during human cutaneous leishmaniasis. However, as senescent cytotoxic CD8⁺ T cells predominate in the skin lesions, they may have a greater role than NK cells in mediating the non-specific skin damage in CL.     

Adoptive transfer of cytomegalovirus‐specific effector CD4+ T cells provides antiviral protection from murine CMV infection

Cytomegalovirus (CMV) infects a majority of the human population and establishes a life‐long persistence. CMV infection is usually asymptomatic but the virus carries pathogenic potential and causes severe disease in immunocompromised individuals. T‐cell‐mediated immunity plays an essential role in control of CMV infection and adoptive transfer of CMV‐specific CD8⁺ T cells restores viral immunity in immunosuppressed patients but a role for CD4⁺ T cells remains elusive. Here, we analyzed in adoptive transfer studies the features and antiviral functions of virus‐specific CD4⁺ T cells during primary murine CMV (MCMV) infection. MCMV‐specific CD4⁺ T cells expanded upon MCMV infection and displayed an effector phenotype and function. Adoptive transfer of in vivo activated MCMV‐specific CD4⁺ T cells to immune‐compromised mice was protective during pathogenic MCMV infection and IFN‐γ was a crucial mediator of this protective capacity. Moreover, co‐transfer of low doses of both MCMV‐specific CD4⁺ T cells and CD8⁺ T cells synergized in control of lytic viral replication in immune‐compromised mice. Our data reveal a pivotal antiviral role for virus‐specific CD4⁺ T cells in protection from pathogenic CMV infection and provide evidence for their antiviral therapeutic potential.     

Alterations in cytotoxic and phenotypic subsets of natural killer cells in acquired immune deficiency syndrome (AIDS)

Testing of cytotoxic function using a panel of natural killer (NK)-sensitive target cells, including a unique herpes simplex virus-infected Raji-cell target, was performed in conjunction with phenotypic cell analysis by dual-color flow cytometry to characterize the NK system. Subjects included in the study were at risk for or infected with the etiologic agent of the acquired immune deficiency syndrome (AIDS), human immunodeficiency virus (HIV). A generalized defect in NK function was temporally correlated with disease manifestations, as evidenced by deficient NK lytic function in patients with AIDS and AIDS-related complex (ARC). Healthy at-risk subjects, including those seropositive for HIV, exhibited robust NK-cell function. Phenotypic analysis revealed that normal proportions of the NK-associated CD16⁺ (Leu11) Leu7^– and CD16⁺(Leu11)Leu7⁺ lymphocyte subsets were maintained throughout the clinical progression of HIV infection. However, the proportion and numbers of cells of the CD8⁺(Leu2)Leu7⁺ subset were increased in AIDS, ARC, and healthy at-risk subjects, including those seronegative for HIV. These results are consistent with a qualitative defect in the NK system in AIDS, perhaps secondary to CD4-cell depletion and a concomitant lack of essential accessory factors. The elevation in CD8⁺(Leu2)/Leu7⁺ cells is not solely the result of HIV infection and may be a general response to viruses and/or other antigenic stimulation.     

Strong and sustained effector function of memory‐ versus naïve‐derived T cells upon T‐cell receptor RNA transfer: Implications for cellular therapy

Current protocols used to select CMV‐specific T cells for adoptive immunotherapy focus on virus‐specific memory T cells from seropositive donors. However, this strategy is not feasible in patients undergoing allogeneic haematopoietic stem‐cell transplantation (HSCT) from CMV‐seronegative donors. Here, we redirected T cells of CMV‐seronegative donors with a human genetically engineered TCR recognizing an HLA‐A*0201‐binding peptide epitope of CMVpp65. To facilitate clinical translation of this approach, we used a non‐viral expression system based on in vitro transcribed RNA and electroporation. Although memory and naïve‐derived T‐cell subsets were both efficiently transfected by TCR‐RNA, memory‐derived T cells showed much stronger levels of HLA‐A*0201‐restricted cytolytic activity to CMV‐infected fibroblasts and maintained acquired function for 5–10 days. In addition to redirection of CD8⁺ cytotoxic T cells, TCR‐RNA transfection was capable of redirecting CD4⁺ T cells into potent Ag‐specific Th cells that efficiently triggered maturation of DCs. Our data suggest that memory rather than naïve‐derived T cells are the preferred subset for transient TCR expression by RNA electroporation, providing more efficient and sustained virus‐specific CD4⁺ and CD8⁺ T‐cell function. CMV TCR‐RNA may represent a suitable therapeutic ‘off‐the‐shelf’ reagent to be used in severe CMV infections of HSCT patients when endogenous CMV‐specific T‐cell immunity is insufficient.     

Characterization of human lymphocyte subpopulations: Alloreactive cytotoxic T-lymphocyte precursor and effector cells are phenotypically distinct from Leu 2+ suppressor cells

The OKT8/Leu 2⁺ human T-cell subset contains cells which perform suppressor and cytotoxic functions. We have recently produced two monoclonal antibodies (termed 2D2 and D12) which define four subpopulations of human E⁺ cells. Previous studies have shown that the Leu 2⁺ cells that suppress T-cell proliferative responses have the 2D2⁺D12⁺ phenotype. In the present studies, we have used these antibodies and fluorescence-activated cell sorter techniques to characterize the phenotype of cytotoxic T lymphocytes generated in allogeneic mixed lymphocyte cultures. These studies indicate that the cytolytic effector cells which recognize class I major histocompatibility antigens express the 2D2⁺D12^– phenotype. The phenotype of the precursor cells for these cytotoxic T cells was similarly demonstrated to be 2D2⁺D12^–. The subset of E⁺ cells with NK cytolytic activity expressed the 2D2^–D12⁺ phenotype. These data demonstrate that the Leu 2⁺ precursor and effector cytotoxic T cells reactive against class I alloantigens are phenotypically distinct from the Leu 2⁺ cells previously shown to suppress T-cell proliferative responses.     

Spotlight on NKG2C and the human NK‐cell response to CMV infection

Immune responses to cytomegalovirus (CMV) infection in the mouse and human involve the expansion of specific subsets of natural killer (NK) cells with specific phenotypic characteristics and a heightened ability to produce interferon (IFN)‐gamma. In humans, these NK‐cell responses are largely driven by the activating receptor NKG2C, which recognize human leukocyte antigen (HLA)‐E in complex with leader sequence peptides. In this issue of the European Journal of Immunology, Noyola et al. [Eur. J. Immunol. 2012, 42: 3256‐3266] examine NK‐cell responses in a unique cohort of young children with asymptomatic and symptomatic congenital CMV infection. They also address NK‐cell responses to CMV in relation to NKG2C gene copy number. Children with a symptomatic congenital infection exhibited a marked expansion of NKG2C⁺ NK cells. However, despite having slightly lower frequencies of NKG2C⁺ NK cells, children with a heterozygous deletion of the NKG2C gene seemed to control the virus as efficiently as those with two copies of the NKG2C gene. The present studies shed new light on the role of NKG2C copy number variation on the human NK‐cell response to CMV infection.     

Early Changes in Frequency of Peripheral Blood Lymphocyte Subpopulations in Severe Traumatic Brain‐Injured Patients

Infections are leading causes of increased morbidity and mortality of severe traumatic brain‐injured (STBI) patients. The mechanism underlying the susceptibility to the infections is still unexplained. The purpose of the study was to investigate changes in frequency of leucocytes subpopulations in peripheral blood of patients with STBI during the course of intensive care treatment. Twenty patients with STBI were included in the study. Healthy age‐ and sex‐ volunteers served as control. Peripheral blood samples were taken from these patients at day 1, 4 and 7, and peripheral blood mononuclear cells (PBMC) were isolated. The percentage of T, B lymphocyte, NK and NKT cells as well as monocytes was analysed by simultaneous detection of surface antigens using fluorochrome‐conjugated monoclonal antibodies. The two major subsets of T lymphocytes (CD3⁺CD56^?CD4⁺ and CD3⁺CD56^?CD8⁺) and NK cells (CD3^?CD56^+dim and CD3^?CD56^+bright) were also analysed by flow cytometry. Extracranial infections were presented in 55% patients with STBI. At day 4, the percentage of T lymphocytes with cytotoxic phenotype significantly diminished and their numbers restored at day 7. The frequency of NKT cells showed the identical time‐dependent pattern, whereas the percentage of NK cells diminished on day 4 but did not restore after 7 days. The frequency of B lymphocytes did not change significantly during the time investigated, whereas the percentage of monocytes increased immediately after the injury and gradually diminished. The decrease in cells with cytotoxic phenotype might explain high incidence of susceptibility to infection of patients with STBI.     

Inhibitory 2B4 contributes to NK cell education and immunological derangements in XLP1 patients

X‐linked lymphoproliferative disease 1 (XLP1) is an inherited immunodeficiency, caused by mutations in SH2D1A encoding Signaling Lymphocyte Activation Molecule (SLAM)‐associated protein (SAP). In XLP1, 2B4, upon engagement with CD48, has inhibitory instead of activating function. This causes a selective inability of cytotoxic effectors to kill EBV‐infected cells, with dramatic clinical sequelae. Here, we investigated the NK cell education in XLP1, upon characterization of killer Ig‐like receptor (KIR)/KIR‐L genotype and phenotypic repertoire of self‐HLA class I specific inhibitory NK receptors (self‐iNKRs). We also analyzed NK‐cell cytotoxicity against CD48⁺ or CD48^? KIR‐ligand matched or autologous hematopoietic cells in XLP1 patients and healthy controls. XLP1 NK cells may show a defective phenotypic repertoire with substantial proportion of cells lacking self‐iNKR. These NK cells are cytotoxic and the inhibitory 2B4/CD48 pathway plays a major role to prevent killing of CD48⁺ EBV‐transformed B cells and M1 macrophages. Importantly, self‐iNKR defective NK cells kill CD48^? targets, such as mature DCs. Self‐iNKR^? NK cells in XLP1 patients are functional even in resting conditions, suggesting a role of the inhibitory 2B4/CD48 pathway in the education process during NK‐cell maturation. Killing of autologous mature DC by self‐iNKR defective XLP1 NK cells may impair adaptive responses, further exacerbating the patients’ immune defect.     

IFN-γ production downstream of NKT cell activation in mice infected with influenza virus enhances the cytolytic activities of both NK cells and viral antigen-specific CD8 T cells

Natural killer T (NKT) cell activation is responsible for eliminating pathogens. However, the biological functions of NKT cells against influenza virus are not fully understood. We therefore investigated the effects of NKT cells in viral infection using CD1d knockout (KO) mice. When CD1d KO or wild-type (WT) mice were infected with a sub-lethal dosage of the influenza virus, the survival rate of CD1d KO mice was significantly lower than for WT mice in association with delayed viral clearance in the lungs. Consistently, IFN-γ production in bronchoalveolar lavage fluid of CD1d KO mice was largely reduced compared to WT mice during infection. Moreover, the cytotoxic activities of NK cells and viral antigen-specific CD8⁺ T cells were impaired in CD1d KO mice. It was concluded that activated NKT cell-induced IFN-γ release enhances both NK-cell activity and antigen-specific CD8⁺ T cells to eliminate the influenza virus, thus leading to an enhanced survival.     

CD38brightCD8+ T Cells Associated with the Development of Acute GVHD Are Activated,Proliferating, and Cytotoxic Trafficking Cells

We have previously reported that a peripheral blood absolute CD38^brightCD8⁺ effector memory T cell (TEM) population expansion of >35 cells/µL predicts the development of acute graft-versus-host disease (GVHD). We hypothesized that these T cells are activated, proliferating, and cytotoxic trafficking cells that are not a response to viral reactivation and may be involved in acute GVHD. We characterized peripheral blood T cell populations at the time of maximum CD38^brightCD8⁺ TEM expansion in patients from our originally reported pediatric allogeneic hematopoietic cell transplantation recipient cohort. Samples were incubated with fluorochrome-conjugated antibodies directed against CD3, CD8, CD38, HLA-DR (T cell activation), Ki-67 (T cell proliferation), granzyme B (marker of cytotoxic T cells), CLA (skin trafficking), CCR5 (visceral trafficking), and CXCR6 (liver trafficking). We also incubated samples with Epstein-Barr virus (EBV) and cytomegalovirus (CMV) peptide pools and measured IFN-γ production by flow cytometry and performed EBV and CMV tetramer staining. Higher median proportions of cell expression of HLA-DR, Ki-67, granzyme B, CLA, CCR5, and CXCR6 were observed for CD38^brightCD8⁺ T cells compared with CD38^nonbrightCD8⁺ T cells in patients with acute GVHD (P < .05) but not in patients without acute GVHD (P not significant). No IFN-γ production was observed after incubation with CMV and EBV peptide pools. EBV-specific tetramer populations of 6.85% and 3.17% were detected in 2 patients with acute GVHD, whereas a CMV-specific tetramer population of 3.77% was detected in 1 patient with acute GVHD. No EBV- or CMV-specific tetramer populations were detected in any patient without acute GVHD. We conclude that CD38^brightCD8⁺ T cells associated with the development of acute GVHD are activated, proliferating, and cytotoxic trafficking cells that do not appear to respond to CMV or EBV reactivation. Further studies are needed to determine whether these cells are directly involved in acute GVHD pathogenesis.