Cytomegalovirus-Associated CD4(+) CD28(null) Cells in NKG2D-Dependent Glomerular Endothelial Injury and Kidney Allograft Dysfunction.

Emerging data suggest that expansion of a circulating population of atypical, cytotoxic CD4(+) T cells lacking costimulatory CD28 (CD4(+) CD28(null) cells) is associated with latent cytomegalovirus (CMV) infection. The purpose of the current study was to increase the understanding of the relevance of these cells in 100 unselected kidney transplant recipients followed prospectively for a median of 54 months. Multicolor flow cytometry of peripheral blood mononuclear cells before transplantation and serially posttransplantation was undertaken. CD4(+) CD28(null) cells were found predominantly in CMV-seropositive patients and expanded in the posttransplantation period. These cells were predominantly effector-memory phenotype and expressed markers of endothelial homing (CX3CR1) and cytotoxicity (NKG2D and perforin). Isolated CD4(+) CD27(-) CD28(null) cells proliferated in response to peripheral blood mononuclear cells previously exposed to CMV-derived (but not HLA-derived) antigens and following such priming incubation with glomerular endothelium resulted in signs of endothelial damage and apoptosis (release of fractalkine and von Willebrand factor; increased caspase 3 expression). This effect was mitigated by NKG2D-blocking antibody. Increased CD4(+) CD28(null) cell frequencies were associated with delayed graft function and lower estimated glomerular filtration rate at end follow-up. This study suggests an important role for this atypical cytotoxic CD4(+) CD28(null) cell subset in kidney transplantation and points to strategies that may minimize the impact on clinical outcomes.

Cytomegalovirus drives Vδ2neg γδ T cell inflation in many healthy virus carriers with increasing age.

Cytomegalovirus (CMV) usually causes lifelong asymptomatic infection, but over time can distort immune profiles. Recent reports describe selective expansion of Vδ2(neg) γδ T cells in healthy and immunocompromised CMV carriers. Having shown previously that virus-specific CD8(+) and CD4(+) T cell responses are increased significantly in elderly CMV carriers, probably driven by chronic stimulation, we hypothesized that Vδ2(neg) γδ T cells may also be expanded with age. Our results show that Vδ2(neg) γδ T cells are increased significantly in CMV-seropositive healthy individuals compared to CMV-seronegative controls in all age groups. The differences were most significant in older age groups (P < 0·0001). Furthermore, while Vδ2(neg) γδ T- cells comprise both naive and memory cells in CMV-seronegative donors, highly differentiated effector memory cells are the dominant phenotype in CMV carriers, with naive cells reduced significantly in numbers in CMV-seropositive elderly. Although phenotypically resembling conventional CMV-specific T cells, Vδ2(neg) γδ T cells do not correlate with changes in magnitude of CMV-specific CD4(+) or CD8(+) T cell frequencies within those individuals, and do not possess ex-vivo immediate effector function as shown by CMV-specific CD4(+) and CD8(+) T cells. However, after short-term culture, Vδ2(neg) γδ T cells demonstrate effector T cell functions, suggesting additional requirements for activation. In summary, Vδ2(neg) γδ T cells are expanded in many older CMV carriers, demonstrating a further level of lymphocyte subset skewing by CMV in healthy individuals. As others have reported shared reactivity of Vδ2(neg) γδ T cells towards tumour cells, the composition of γδ T cell subsets may also have implications for risk of developing cancer in elderly people.

Proliferation-based T-cell selection for immunotherapy and graft-versus-host-disease prophylaxis in the context of bone marrow transplantation.

Graft-versus-host disease (GvHD) caused by alloreactive T cells within the graft is a major drawback of allogeneic BMT, but depletion of T cells leads to higher rates of relapse, opportunistic infections and graft failure. Therefore, selective removal of GvHD-inducing alloreactive T cells might be beneficial. We describe here the separation of alloresponsive T cells, based on carboxyfluorescein succimidyl ester labeling, in vitro allostimulation and FACS-sorting. In vivo effects of the separated cell populations were investigated in the context of allogeneic BMT in murine models: in vitro resting T cells were shown to survive in the allogeneic host and retain immunoreactivity against 'third-party' antigens. As demonstrated in two different transplantation models, elimination of proliferating cells significantly reduces GvHD but offers no advantages to using T-cell-depleted bone marrow alone concerning engraftment and tumor control. Transplanting T cells that proliferate in response to tumor antigens in vitro may narrow down the spectrum of antigens recognized by T cells and therefore reduce GvHD while maintaining graft-facilitating function and tumor control. Therefore, selecting tumor-reactive T cells on the basis of their proliferative response in vitro may be beneficial for the recipient, less time consuming than T-cell cloning and still reduce the extent of GvHD.

Gene expression induced by interleukin-17 in fibroblast-like synoviocytes of patients with rheumatoid arthritis: upregulation of hyaluronan-binding protein TSG-6.

Interleukin-17 (IL-17) has been characterized as a proinflammatory cytokine produced by CD4+ CD45RO+ memory T cells. Overproduction of IL-17 was detected in the synovium of patients with rheumatoid arthritis (RA) compared with patients with osteoarthritis. This study examines differentially expressed genes after the stimulation of fibroblast-like synoviocytes of RA patients by IL-17. Among these genes we identified the following: tumor necrosis factor-stimulated gene-6 (TSG-6), IL-6, IL-8, GRO-beta, and bone morphogenetic protein-6 with an expression 3.6-10.6-fold that in the unstimulated control. IL-17 augmented the expression of TSG-6, a hyaluronan-binding protein, in a time- and dose-dependent manner. IL-17 showed additive effects with IL-1beta and tumour necrosis factor-alpha on the expression of TSG-6, IL-6 and IL-8. The mitogen-activated protein kinase p38 seems to be necessary for the regulation of TSG-6 expression by IL-17, as shown by inhibition with SB203580. Our results support the hypothesis that IL-17 is important in the pathogenesis of RA, contributing to an unbalanced production of cytokines as well as participating in connective tissue remodeling.