Interferon-γ (IFNγ) is an important mediator of cellular immune responses, but high systemic levels of this cytokine are associated with immunopathology. IFNγ binds to its receptor (IFNγR) and to extracellular matrix (ECM) via four positively charged C-terminal amino acids (KRKR), the ECM-binding domain (EBD). Across evolution, IFNγ is not well conserved, but the EBD is highly conserved, suggesting a critical function. Here, we show that IFNγ lacking the EBD (IFNγΔKRKR) does not bind to ECM but still binds to the IFNγR and retains bioactivity. Overexpression of IFNγΔKRKR in tumors reduced local ECM binding, increased systemic levels and induced sickness behavior, weight loss and toxicity. To analyze the function of the EBD during infection, we generated IFNγΔKRKR mice lacking the EBD by using CRISPR-Cas9. Infection with lymphocytic choriomeningitis virus resulted in higher systemic IFNγΔKRKR levels, enhanced sickness behavior, weight loss and fatal toxicity. We conclude that local retention of IFNγ is a pivotal mechanism to protect the organism from systemic toxicity during prolonged immune stimulation.
© 2023. The Author(s).

Thymic selection and peripheral activation of conventional T (Tconv) and regulatory T (Treg) cells depend on TCR signaling, whose anomalies are causative of autoimmunity. Here, we expressed in normal mice mutated ZAP-70 molecules with different affinities for the CD3 chains, or wild type ZAP-70 at graded expression levels under tetracycline-inducible control. Both manipulations reduced TCR signaling intensity to various extents and thereby rendered those normally deleted self-reactive thymocytes to become positively selected and form a highly autoimmune TCR repertoire. The signal reduction more profoundly affected Treg development and function because their TCR signaling was further attenuated by Foxp3 that physiologically repressed the expression of TCR-proximal signaling molecules, including ZAP-70, upon TCR stimulation. Consequently, the TCR signaling intensity reduced to a critical range generated pathogenic autoimmune Tconv cells and concurrently impaired Treg development/function, leading to spontaneous occurrence of autoimmune/inflammatory diseases, such as autoimmune arthritis and inflammatory bowel disease. These results provide a general model of how altered TCR signaling evokes autoimmune disease.
© 2022 Tanaka et al.

Deletion of the gene for Themis affects T cell selection in the thymus, which would be expected to affect the TCR repertoire. We found an increased proportion of cells expressing Vα3.2 (TRAV9N-3) in the peripheral CD8+ T cell population in mice with germline Themis deficiency. Analysis of the TCRα repertoire indicated it was generally reduced in diversity in the absence of Themis, whereas the diversity of sequences using the TRAV9N-3 V-region element was increased. In wild type mice, Vα3.2+ cells showed higher CD5, CD6 and CD44 expression than non-Vα3-expressing cells, and this was more marked in cells from Themis-deficient mice. This suggested a virtual memory phenotype, as well as a stronger response to self-pMHC. The Vα3.2+ cells responded more strongly to IL-15, as well as showing bystander effector capability in a Listeria infection. Thus, the unusually large population of Vα3.2+ CD8+ T cells found in the periphery of Themis-deficient mice reflects not only altered thymic selection, but also allowed identification of a subset of bystander-competent cells that are also present in wild-type mice.
Copyright © 2021 Prasad, Wojciech, Brzostek, Hu, Chua, Tung, Yap, Rybakin and Gascoigne.

To investigate the role of TCR-pMHC interaction in regulating lung CD8 tissue-resident T cell (TR ) differentiation, polyclonal responses were compared against NP366-374 /Db and PA224-233 /Db , two immunodominant epitopes that arise during influenza A infection in mice. Memory niches distinct from iBALTs develop within the lamina propria, supporting CD103+ and CD103- CD8 TR generation and intraepithelial translocation. Gene set enrichment analysis (GSEA) and weighted gene co-expression network analysis (WGCNA) identify dominant TCR, adherens junction, RIG-I-like and NOD-like pattern recognition receptor as well as TGF-β signaling pathways and memory signatures among PA224-233 /Db T cells consistent with T resident memory (TRM ) status. In contrast, NP366-374 /Db T cells exhibit enrichment of effector signatures, upregulating pro-inflammatory mediators even among TRM . While NP366-374 /Db T cells manifest transcripts linked to canonical exhaustion pathways, PA224-233 /Db T cells exploit P2rx7 purinoreceptor attenuation. The NP366-374 /Db CD103+ subset expresses the antimicrobial lactotransferrin whereas PA224-233 /Db CD103+ utilizes pore-forming mpeg-1, with <22% of genes correspondingly upregulated in CD103+ (or CD103- ) subsets of both specificities. Thus, TCR-pMHC interactions among TR and antigen presenting cells in a tissue milieu strongly impact CD8 T cell biology.
© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

CD4(+) T cells play a critical role in determining the disease outcome in murine cutaneous leishmaniasis, and selective usage of T-cell receptor (TCR) is implied in promoting Leishmania major infection. However, little information is available on TCR usage in Leishmania-specific, IFN-γ-producing CD4(+) T cells. In this study, we investigated the TCR diversity and activation of CD4(+) T cells in a nonhealing model associated with L. amazonensis (La) infection and a self-healing model associated with L. braziliensis (Lb) infection. While marked expansion in the absolute number of several subsets was observed in Lb-infected mice, the percentages of TCR Vβ(+) CD4(+) -cell subsets were comparable in draining LN- and lesion-derived T cells in two infection models. We found that multiple TCR Vβ CD4(+) T cells contributed collectively and comparably to IFN-γ production and that the overall levels of IFN-γ production positively correlated with the control of Lb infection. Moreover, pre-infection with Lb parasites provided cross-protection against secondary La infection, owing to an enhanced magnitude of T-cell activation and IFN-γ production. Collectively, this study suggests that the magnitude of CD4(+) T-cell activation, rather than the TCR diversity, is the major determining factor for the outcome of Leishmania infection.
© 2011 Blackwell Publishing Ltd.