Circulating Vitamin D (Vit-D) has emerged as a potent immune modulator in asthma, yet its direct impact on TH2 cell regulation, the central effectors of allergic inflammation, remains unclear. Preliminary transcriptomic analysis of neonatal cord blood revealed that gestational Vit-D deficiency corresponds to elevated adaptive and innate immune responses, driven by TH2 immunity and antimicrobial responses related to asthma inflammation. To elucidate cell-specific molecular mechanisms of Vit-D, we differentiated murine TH2 cells in vitro under conditions mimicking Vit-D sufficiency and deficiency. Our findings demonstrate that Vit-D exposure promotes intracellular calcium ion homeostasis while suppressing prominent inflammatory cytokines characteristic of asthma. Conversely, Vit-D deficiency reprograms TH2 cell lineage commitment, inducing overexpression of cytolytic molecules and major histocompatibility complex (MHC) class I molecules-traits typically associated with cytotoxicity rather than the canonical helper function. Our findings underscore Vit-D's role in stabilizing TH2 cell function and fate, offering insights into asthma and autoimmune disorders.
© 2025 The Authors.

CD8+ T cells are a crucial part of the adaptive immune system, responsible for combating intracellular pathogens and tumor cells. The initial activation of T cells involves the formation of highly dynamic Ca2+ microdomains. Recently, purinergic signaling was shown to be involved in the formation of the initial Ca2+ microdomains in CD4+ T cells. In this study, the role of purinergic cation channels, particularly P2X4 and P2X7, in CD8+ T cell signaling from initial events to downstream responses was investigated, focusing on various aspects of T cell activation, including Ca2+ microdomains, global Ca2+ responses, NFAT-1 translocation, cytokine expression, and proliferation. While Ca2+ microdomain formation was significantly reduced in the first milliseconds to seconds in CD8+ T cells lacking P2X4 and P2X7 channels, global Ca2+ responses over minutes were comparable between wild-type (WT) and knockout cells. However, the onset velocity was reduced in P2X4-deficient cells, and P2X4, as well as P2X7-deficient cells, exhibited a delayed response to reach a certain level of free cytosolic Ca2+ concentration ([Ca2+]i). NFAT-1 translocation, a crucial transcription factor in T cell activation, was also impaired in CD8+ T cells lacking P2X4 and P2X7. In addition, the expression of IFN-γ, a major pro-inflammatory cytokine produced by activated CD8+ T cells, and Nur77, a negative regulator of T cell activation, was significantly reduced 18h post-stimulation in the knockout cells. In line, the proliferation of T cells after 3 days was also impaired in the absence of P2X4 and P2X7 channels. In summary, the study demonstrates that purinergic signaling through P2X4 and P2X7 enhances initial Ca2+ events during CD8+ T cell activation and plays a crucial role in regulating downstream responses, including NFAT-1 translocation, cytokine expression, and proliferation on multiple timescales. These findings suggest that targeting purinergic signaling pathways may offer potential therapeutic interventions.
Copyright © 2024 Brock, Lory, Möckl, Birus, Stähler, Woelk, Jaeckstein, Heeren, Koch-Nolte, Rissiek, Mittrücker, Guse, Werner and Diercks.

Enrichment for tyrosine in immunoglobulin CDR-H3 is due in large part to natural selection of germline immunoglobulin DH sequence. We have previously shown that when DH sequence is modified to reduce the contribution of tyrosine codons, epitope recognition is altered and B cell development, antibody production, autoantibody production, and morbidity and mortality following pathogen challenge are adversely affected. TCRβ diversity (Dβ) gene segment sequences are even more highly conserved than DH, with trout Dβ1 identical to human and mouse Dβ1. We hypothesized that natural selection of Dβ sequence also shapes CDR-B3 diversity and influences T cell development and T cell function. To test this, we used a mouse strain that lacked Dβ2 and contained a novel Dβ1 allele (DβYTL) that replaces Dβ1 with an immunoglobulin DH, DSP2.3. Unlike Dβ1, wherein glycine predominates in all three reading frames (RFs), in DSP2.3 there is enrichment for tyrosine in RF1, threonine in RF2, and leucine in RF3. Mature T cells using DβYTL expressed TCRs enriched at particular CDR-B3 positions for tyrosine but depleted of leucine. Changing Dβ sequence altered thymocyte and peripheral T cell numbers and the T cell response to an ovalbumin immunodominant epitope. The differences in tyrosine content might explain, at least in part, why TCRs are more polyspecific and of lower affinity for their cognate antigens than their immunoglobulin counterparts.
Copyright © 2020 Levinson, Khass, Burrows and Schroeder.

We have previously shown that the sequence of the immunoglobulin diversity gene segment (D H ) helps dictate the structure and composition of complementarity determining region 3 of the immunoglobulin heavy chain (CDR-H3). In order to test the role of germline D sequence on the diversity of the preimmune TCRβ repertoire of T cells, we generated a mouse with a mutant TCRβ DJC locus wherein the Dβ2-Jβ2 gene segment cluster was deleted and the remaining diversity gene segment, Dβ1 (IMGT:TRDB1), was replaced with DSP2.3 (IMGT:IGHD2-02), a commonly used B cell immunoglobulin D H gene segment. Crystallographic studies have shown that the length and thus structure of TCR CDR-B3 places amino acids at the tip of CDR-B3 in a position to directly interact with peptide bound to an MHC molecule. The length distribution of complementarity determining region 3 of the T cell receptor beta chain (CDR-B3) has been proposed to be restricted largely by MHC-specific selection, disfavoring CDR-B3 that are too long or too short. Here we show that the mechanism of control of CDR-B3 length depends on the Dβ sequence, which in turn dictates exonucleolytic nibbling. By contrast, the extent of N addition and the variance of created CDR3 lengths are regulated by the cell of origin, the thymocyte. We found that the sequence of the D and control of N addition collaborate to bias the distribution of CDR-B3 lengths in the pre-immune TCR repertoire and to focus the diversity provided by N addition and the sequence of the D on that portion of CDR-B3 that is most likely to interact with the peptide that is bound to the presenting MHC.
Copyright © 2020 Khass, Levinson, Schelonka, Kapoor, Burrows and Schroeder.

Immunological homeostasis in T cells is maintained by a tightly regulated signaling and transcriptional network. Full engagement of effector T cells occurs only when signaling exceeds a critical threshold that enables induction of immune response genes carrying an epigenetic memory of prior activation. Here we investigate the underlying mechanisms causing the suppression of normal immune responses when T cells are rendered anergic by tolerance induction. By performing an integrated analysis of signaling, epigenetic modifications, and gene expression, we demonstrate that immunological tolerance is established when both signaling to and chromatin priming of immune response genes are weakened. In parallel, chromatin priming of immune-repressive genes becomes boosted, rendering them sensitive to low levels of signaling below the threshold needed to activate immune response genes. Our study reveals how repeated exposure to antigens causes an altered epigenetic state leading to T cell anergy and tolerance, representing a basis for treating auto-immune diseases.
Copyright © 2020 The Author(s). Published by Elsevier Inc. All rights reserved.