Biology subjects

Castro, T. B. R.

Publications and source records attributed to Castro, T. B. R..

4 recordsLinked to original sources

bioRxiv2026

Weaning imprints a hybrid cytotoxic-regulatory identity on intestinal CD4+ T lymphocytes

The intestinal immune system must adapt as the neonatal gut shifts from milk to solid food and becomes densely colonized. How the T cell compartment is established under these conditions remains unclear. Using fate-mapping to timestamp naive T cells, with imaging, transcriptomic, and repertoire analyses, we tracked them from suckling to adulthood. Intestinal T cell entry peaked at weaning, coinciding with relocation from crypts to villi guided by the tissue microenvironment and, partly, the microbiota. T cells timestamped at suckling persisted into adulthood and, at weaning, adopted a transient cytotoxic-regulatory state in the lamina propria, with granzyme B expression microbiota-dependent only in the ileum. Clonal expansions at weaning were restricted to the small intestinal lamina propria and absent in germ-free mice. Most expanded clones recognized early-life commensals. Weaning is a physiological window of transient inflammation imprinting a hybrid CD4 T cell compartment, suggesting that early-life commensals modulate T cell selection.

immunology↗

bioRxiv2023

Suppression of epithelial proliferation and tumorigenesis by immunoglobulin A

Immunoglobulin A (IgA) is the most abundant antibody isotype produced across mammals and plays a specialized role in mucosal homeostasis1. Constantly secreted into the lumen of the intestine, IgA binds commensal microbiota to regulate their colonization and function2,3 with unclear implications for health. IgA deficiency is common in humans but is difficult to study due to its complex aetiology and comorbidities4-8. Using genetically and environmentally controlled mice, here we show that IgA-deficient animals have increased susceptibility to endogenous colorectal tumours. Cellular and molecular analyses revealed that, in the absence of IgA, colonic epithelial cells induce antibacterial factors and accelerate cell cycling in response to the microbiota. Oral treatment with IgA was sufficient to both reduce steady-state proliferation and protect mice from tumours, but this function was due to antibody structure rather than binding specificity. In both organoid and monolayer culture systems, IgA directly suppressed epithelial growth. Co-immunoprecipitation mass spectrometry and a targeted CRISPR screen identified DMBT1 as an IgA-binding epithelial surface protein required for IgA-mediated suppression of proliferation. Together, IgA and DMBT1 regulate Notch signalling and tune the normal cycling of absorptive colonocyte progenitors. In mice, deleting the transmembrane and cytoplasmic signalling portions of DMBT1 or blocking Notch signalling was sufficient to reverse both the increased proliferation and tumour susceptibility of IgA knockouts. These experiments establish a homeostatic function for IgA in tempering physiological epithelial responses to microbiota to maintain mucosal health.

immunology↗

bioRxiv2020

T cell receptor is required for differentiation but not maintenance of intestinal intraepithelial lymphocytes

The gut epithelium is populated by intraepithelial lymphocytes (IELs), a heterogeneous T cell population with cytotoxic and regulatory properties. Migrating peripheral CD4+ T cells, including regulatory (Treg) and conventional T cells (Tconv), acquire an IEL (CD4-IEL) program upon arrival at the epithelium. However, the specific role of the T cell receptor (TCR) in this process remains unclear. Single-cell TCR repertoire and transcriptomic analysis of intraepithelial CD4+ T cells revealed different extents of clonal expansion and TCR overlap between cell states; fully differentiated CD4-IELs from Tregs or Tconvs were the least diverse. Conditional deletion of TCR on differentiating CD4+ T cells or of MHCII on intestinal epithelial cells prevented CD4-IEL differentiation. However, TCR ablation on developed CD4-IELs did not affect their accumulation. These results indicate that local recognition of a limited set of antigens is an essential signal for the differentiation and adaptation of T cells to the epithelium.

immunology↗

bioRxiv2020

Stepwise chromatin and transcriptional acquisition of an intraepithelial lymphocyte program

Mesenteric lymph node (mLN) T cells undergo tissue adaptation upon migrating to intestinal lamina propria (LP) and intraepithelial (IE) compartments, ensuring appropriate balance between tolerance and resistance. By combining mouse genetics with single-cell and chromatin analyses, we addressed the molecular imprinting of gut epithelium on T cells. Transcriptionally, conventional and regulatory (Treg) CD4+ T cells from mLN, LP and IE segregate based on the gut layer they occupy; trajectory analysis suggests a stepwise loss of CD4-programming and acquisition of an intraepithelial profile. Treg fate-mapping coupled with RNA- and ATAC-sequencing revealed that the Treg program shuts down before an intraepithelial program becomes fully accessible at the epithelium. Ablation of CD4 lineage-defining transcription factor ThPOK results in premature acquisition of an IEL profile by mLN Tregs, partially recapitulating epithelium imprinting. Thus, coordinated replacement of circulating lymphocyte program with site-specific transcriptional and chromatin changes is necessary for tissue imprinting.

immunology↗