Biology subjects

Premo, K.

Publications and source records attributed to Premo, K..

3 recordsLinked to original sources

bioRxiv2025

Multimodal analysis defines GNG4 as a distinguishing feature of germinal center-positioned CD4 T follicular helper cells in humans

CD4 T follicular helper (Tfh) cells coordinate humoral immune responses within germinal centers (GC) of lymphoid tissue. Despite their critical roles in vaccination and autoimmunity, the gene expression programs that define functionally distinct human Tfh states-- and the molecular pathways engaged by Tfh positioned within the GC niche--remain incompletely understood. This gap has limited translational efforts to monitor or therapeutically target specific Tfh states for clinical benefit. Here, we delineate human CD4 T cell heterogeneity in tonsils and peripheral blood using trimodal single-cell sequencing and spectral flow cytometry to define epigenomic, transcriptional, and proteomic features of distinct Tfh states. Tfh with a GC-like phenotype exhibited markedly increased chromatin accessibility and both mRNA and protein expression of G protein subunit gamma 4 (GNG4). In tonsil, single-cell spatial transcriptomics defined GNG4 expression as a distinguishing feature of activated Tfh states within spatially demarcated GC compartments, with greater specificity than conventionally GC-associated features such as BCL6, TOX2, and S1PR2. In contrast, GNG4- Tfh primarily localized to nonGC regions and exhibited a resting, Th17-polarized phenotype. Together, these data highlight GNG4 as a central feature of activated, GC-positioned Tfh cell identity in humans. One Sentence SummaryGNG4 expression defines activated CD4 T follicular helper cells localized to the germinal center of human lymphoid tissue.

immunology↗

bioRxiv2025

Loss of B cell tolerance at the T2/T3a B cell transition is a convergent pathogenic mechanism in common variable immunodeficiency

Many patients with common variable immunodeficiency (CVID), including those with CTLA4 deficiency, NFKB1 variants and activated PI3K-delta syndrome (APDS), develop autoimmunity that is refractory to treatment. Despite this shared clinical phenotype, a unifying mechanism for the breakdown of B cell tolerance across monogenic forms of CVID has not been established. Here, we demonstrate that patients with loss-of-function NFKB1 variants, like those with CTLA4 variants and APDS, exhibit dysregulated CD4+ T cell expansion, accumulation of transitional B cells, and a relative lack of follicular B cells. In patients with monogenic CVID and clinical autoimmunity, we observed a relative expansion of transitional and activated naive (aN: CD21loCD11chi) B cells in peripheral blood accompanied by a marked increase in the frequency of VH4-34 expressing autoreactive 9G4+ B cells, which expanded between T2 and T3a transitional B cell stages. Single-cell transcriptomic and B cell receptor analysis further revealed a marked expansion of activated T1/2, T3 and extrafollicular activated naive and double negative (DN: IgD-CD27-) B cell subsets in APDS patients. Notably, one B cell subset appeared exclusively in the APDS disease state, characterized by high oxidative phosphorylation in transitional B cells, specifically. In APDS patients, we also observed a clonal expansion of specific extrafollicular class-switched DN B cells, which were clonally derived from activated transitional B cells. DN B cells were also identified in APDS lung tissue, consistent with the contribution of activated, extrafollicularly-derived B cells to tissue inflammation. Together, these findings suggest that in many patients with CVID and autoimmune features, premature activation of autoreactive transitional T2 and T3a B cells induces the survival and expansion, rather than the tolerization and elimination, of self-reactive B cells. This process leads to extrafollicular expansion of autoreactive B cells capable of tissue infiltration. One Sentence SummaryLoss of transitional B cell tolerance and extrafollicular expansion of autoreactive B cells drive autoimmunity in monogenic causes of CVID.

immunology↗

bioRxiv2024

Congenital T cell activation impairs transitional to follicular B cell maturation in humans

CTLA4-deficient patients exhibit profound humoral immune dysfunction, yet the basis for the B cell defect is not known. We observed a marked reduction in transitional to follicular B cell development in CTLA4-deficient patients, correlating with decreased CTLA4 function in regulatory T cells and increased mTORC1 signaling in transitional B cells. Treatment of transitional B cells with CD40L was sufficient to induce mTORC1 signaling and inhibit follicular B cell maturation in vitro. Frequent cell-cell contacts between CD40L+ T cells and naive IgD+CD27- B cells were observed in patient lymph nodes. Follicular B cell maturation in CTLA-deficient patients was partially rescued following CTLA4 replacement therapy in vivo. We conclude that functional regulatory T cells and the containment of excessive T cell activation are required for follicular B cells to mature and attain metabolic quiescence and thus acquire a state of immunological self-tolerance. One Sentence SummaryCongenital T cell activation in CTLA4-deficient patients impairs transitional to follicular B cell maturation and can be rescued by CTLA4 replacement therapy in vivo.

immunology↗