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Central memory T cells (TCM) patrol lymph nodes, providing central immunosurveillance against known pathogens, but have not been described as conducting primary tissue immunosurveillance. We analyzed the expression of tissue-homing addressins in human TCM vs effector memory T cells (TEM) from the same donors. In humans, the majority of human TCM were tropic for either skin or gut, and the overall tissue tropism of TCM was comparable to that of TEM TCM were present in healthy, noninflamed human skin, lung, colon, and cervix, suggesting a role for TCM in the primary immunosurveillance of peripheral tissues. TCM also had potent effector functions; 80% of CD8+ TCM produced TC1/TC2/TC17/TC22 cytokines. TCM injected into human skin-grafted mice migrated into skin and induced inflammatory eruptions comparable to TEM-injected mice. In summary, human TCM express peripheral tissue-homing receptors at levels similar to their effector memory counterparts, are found in healthy human tissues, have impressive effector functions, and can act alone to induce skin inflammation in human engrafted mice. Our studies support a novel role for human TCM in primary immunosurveillance of peripheral tissues and highlight the important role of this long-lived cell type in tissue-based immune responses.

Graft-versus-host disease (GVHD) is a major cause of morbidity and mortality in hematopoietic stem cell transplantation (HSCT). Donor T cells are key mediators in pathogenesis, but a contribution from host T cells has not been explored, as conditioning regimens are believed to deplete host T cells. To evaluate a potential role for host T cells in GVHD, the origin of skin and blood T cells was assessed prospectively in patients after HSCT in the absence of GVHD. While blood contained primarily donor-derived T cells, most T cells in the skin were host derived. We next examined patient skin, colon, and blood during acute GVHD. Host T cells were present in all skin and colon acute GVHD specimens studied, yet were largely absent in blood. We observed acute skin GVHD in the presence of 100% host T cells. Analysis demonstrated that a subset of host T cells in peripheral tissues were proliferating ([Ki67.sup.+]) and producing the proinflammatory cytokines IFN-[gamma] and IL-17 in situ. Comparatively, the majority of antigen-presenting cells (APCs) in tissue in acute GVHD were donor derived, and donor-derived APCs were observed directly adjacent to host T cells. A humanized mouse model demonstrated that host skin-resident T cells could be activated by donor monocytes to generate a GVHD-like dermatitis. Thus, host tissue-resident T cells may play a previously unappreciated pathogenic role in acute GVHD., Introduction Graft-versus-host disease (GVHD) is a major cause of morbidity and mortality in hematopoietic stem cell transplantation (HSCT) (1-6). Current dogma holds that donor T cells, either transferred with or [...]

This study examines the effectiveness of macroprudential policies in reducing the banks' risk during the COVID‐19 pandemic and compares these results with the systemic banking crises years. Based on a sample of 624 banks across 40 countries during the period 2006–2020, we find that loosening capital‐aimed macroprudential policies effectively reduced banks' risk during the COVID‐19 pandemic, while this behavior led to increased risk during the systemic crises years. In contrast, tightening the remaining macroprudential policies during the systemic crises years and during the pandemic proved effective in reducing banks' risk. Furthermore, we show that the magnitude of the impact of macroprudential policies was stronger during the systemic crisis than that during the pandemic. Finally, we show that the results are driven by the capital requirement prudential policy, both during the systemic crisis and the COVID‐19 pandemic, although the conservation buffer and the leverage limit also contributes to the ineffectiveness of these policies during the COVID‐19 pandemic. The banks' leverage and loan growth also play an enhancing role of the effects of the macroprudential policies. [ABSTRACT FROM AUTHOR]

In psoriasis, an IL-17-mediated inflammatory skin disease, skin lesions resolve with therapy, but often recur in the same locations when therapy is discontinued. We propose that residual T cell populations in resolved psoriatic lesions represent the pathogenic T cells of origin in this disease. Utilizing high-throughput screening (HTS) of the T cell receptor (TCR) and immunostaining, we found that clinically resolved psoriatic lesions contained oligoclonal populations of T cells that produced IL-17A in both resolved and active psoriatic lesions. Putative pathogenic clones preferentially utilized particular V[beta] and V[alpha] subfamilies. We identified 15 TCR[beta] and 4 TCR[alpha] antigen receptor sequences shared between psoriasis patients and not observed in healthy controls or other inflammatory skin conditions. To address the relative roles of [alpha][beta] versus [gamma][delta] T cells in psoriasis, we carried out TCR/8 HTS. These studies demonstrated that the majority of T cells in psoriasis and healthy skin are [alpha][beta] T cells. [gamma][delta] T cells made up 1% of T cells in active psoriasis, less than 1% in resolved psoriatic lesions, and less than 2% in healthy skin. All of the 70 most frequent putative pathogenic T cell clones were [alpha][beta] T cells. In summary, IL-17-producing [alpha][beta] T cell clones with psoriasis-specific antigen receptors exist in clinically resolved psoriatic skin lesions. These cells likely represent the disease-initiating pathogenic T cells in psoriasis, suggesting that lasting control of this disease will require suppression of these resident T cell populations., Introduction Psoriasis is a T cell- and IL-17-mediated inflammatory skin disease, characterized by inflamed skin lesions and systemic complications as well as arthritis in some patients (1, 2). Psoriatic skin [...]