In humans, all αβ CD8+ T cells express NKG2D, but in mouse, it is only expressed by activated and memory CD8+ T cells. We purified human naive CD8+ T cells to show that NKG2D serves as a costimulatory receptor for TCR induced Ca2+ mobilization and proliferation. The resulting effector cells are skewed toward a type 1 phenotype and produce high levels of IFN-γ and TNF-α. NKG2D ligands, MHC class I chain-related (MIC)A, MICB, and UL16-binding proteins are expressed on the proliferating cells and NKG2D is down-regulated. The addition of the homeostatic cytokines IL-7 and IL-15 to the culture medium not only enhances proliferation but also counteracts the down-regulation of NKG2D, more so than the addition of IL-2. These results indicate that NKG2D can regulate the priming of human naive CD8+ T cells, which may provide an alternative mechanism for potentiating and channeling the immune response.

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Immune responses must be tightly regulated to avoid hyporesponsiveness on one hand or excessive inflammation and the development of autoimmunity (hyperresponsiveness) on the other hand. This balance is attained through the throttling of activating signals by inhibitory signals that ideally leads to an adequate immune response against an invader without excessive and extended inflammatory signals that promote the development of autoimmunity. The CD94/NKG2 family of receptors is composed of members with activating or inhibitory potential. These receptors are expressed predominantly on NK cells and a subset of CD8+ T cells, and they have been shown to play an important role in regulating responses against infected and tumorigenic cells. In this review, we discuss the current knowledge about this family of receptors, including ligand and receptor interaction, signaling, membrane dynamics, regulation of gene expression and their roles in disease regulation, infections, and cancer, and bone marrow transplantation.

IL-21 is a recently described cytokine, produced by activated Th cells, that shares significant homology with members of the IL-2 family of cytokines. IL-21 mediates its biological effects via the IL-21R in conjunction with the common receptor γ-chain that is also shared by members of the IL-2 family. We report that culture of human primary NK and CD8+ T cells with IL-21 in combination with IL-2 results in significant reduction of the cell surface expression of NKG2D, compared with that in cells treated with IL-2 alone. The reduced expression of NKG2D after IL-21 culture had functional consequences for NK cell function, as assessed by NKG2D-mediated redirected lysis assays and degranulation assays, compared with NK cells treated with IL-2 alone. IL-21-mediated NKG2D down-regulation in human NK cells correlated with a marked reduction of DNAX-activating protein of 10 kDa (DAP10) transcription in cells treated with IL-2 in combination with IL-21 compared with cells stimulated with only IL-2. This was attributed to a dramatic reduction in DAP10 promoter activity, as assessed by a DAP10 luciferase reporter construct. In contrast to NKG2D expression, IL-21 was able to induce the expression of the NK activation receptors NKp30 and 2B4 as well as the costimulatory receptor CD28 on CD8+ T cells. These data indicate that IL-21 is able to channel NK and CD8+ T cell function by altering the expression pattern of activation/costimulatory receptors.

T cell cytokines contribute to immunity against Staphylococcus aureus, but the predominant T cell subsets involved are unclear. In an S. aureus skin infection mouse model, we found that the IL-17 response was mediated by γδ T cells, which trafficked from lymph nodes to the infected skin to induce neutrophil recruitment, proinflammatory cytokines IL-1α, IL-1β, and TNF, and host defense peptides. RNA-seq for TRG and TRD sequences in lymph nodes and skin revealed a single clonotypic expansion of the encoded complementarity-determining region 3 amino acid sequence, which could be generated by canonical nucleotide sequences of TRGV5 or TRGV6 and TRDV4. However, only TRGV6 and TRDV4 but not TRGV5 sequences expanded. Finally, Vγ6+ T cells were a predominant γδ T cell subset that produced IL-17A as well as IL-22, TNF, and IFNγ, indicating a broad and substantial role for clonal Vγ6+Vδ4+ T cells in immunity against S. aureus skin infections.

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Background: Pyoderma gangrenosum (PG) is a debilitating ulcerative skin disease that is one of the most common associated diseases seen in patients with inflammatory bowel disease and rheumatoid arthritis. Although PG is classified as a neutrophilic dermatosis, its pathophysiology is poorly understood.objective: Use data obtained from patient-reported histories, immunohistochemistry, and gene expression analysis to formulate a hypothesis on PG pathophysiology.Methods: Ten PG patients participated and answered questions about new ulcer formation. Skin biopsies of healed prior ulcers and adjacent normal skin were obtained from four patients for immunohistochemistry. Scars from healthy patients and patients with discoid lupus were used as additional controls. New onset PG papules were analyzed using immunohistochemistry and gene expression analysis via quantitative real-time PCR.results: All PG patients reported that healed sites of previous ulceration are refractory to re-ulceration. Simultaneous biopsies of healed and uninvolved skin triggered ulceration only in the latter. On immunohistochemistry, healed PG scars showed complete loss of pilosebaceous units, which were present in normal skin, and to a lesser extent in control scars, and discoid scars. Early PG papules showed perivascular and peripilosebaceous T cell infiltrates, rather than neutrophils. These early inflammatory events were dominated by increased gene expression of CXCL9, CXCL10, CXCL11, IFNG, and transcription factors consistent with Th1 phenotype.Limitations: Small sample size was the main limitation. Conclusion:We put forth the hypothesis that PG is a T cell response resulting in the destruction of pilosebaceous units.

Changes in cell surface glycosylation occur during the development and differentiation of cells and have been widely correlated with the progression of several diseases. Because of their structural diversity and sensitivity to intra-and extracellular conditions, glycans are an indispensable tool for analyzing cellular transformations. Glycans present on the surface of intestinal epithelial cells (IEC) mediate interactions with billions of native microorganisms, which continuously populate the mammalian gut. A distinct feature of IECs is that they differentiate as they migrate upwards from the crypt base to the villus tip. In this study, nano-LC/ESI QTOF MS profiling was used to characterize the changes in glycosylation that correspond to Caco-2 cell differentiation. As Caco-2 cells differentiate to form a brush border membrane, a decrease in high mannose type glycans and a concurrent increase in fucosylated and sialylated complex/hybrid type glycans were observed. At day 21, when cells appear to be completely differentiated, remodeling of the cell surface glycome ceases. Differential expression of glycans during IEC maturation appears to play a key functional role in regulating the membrane-associated hydrolases and contributes to the mucosal surface innate defense mechanisms. Developing methodologies to rapidly identify changes in IEC surface glycans may lead to a rapid screen-