Biology subjects

Kastenschmidt, J. M.

Publications and source records attributed to Kastenschmidt, J. M..

4 recordsLinked to original sources

bioRxiv2026

Divergent phenotypic and functional roles of human T follicular helper cells from infancy to adulthood

Antibody responses to T-dependent antigens are suboptimal in young children, yet the evolution of T follicular helper cell (Tfh) function across the human lifespan remains poorly defined. Using human tonsils, a physiologically relevant and abundant source of Tfh, we investigated age-associated differences in their repertoire and functional programs. Pediatric tonsils were enriched for cytokine-expressing Tfh subsets with increased clonal diversity and phenotypic plasticity. However, in response to influenza antigens, they exhibited reduced Th1 polarization, diminished IL-21 production, and limited B cell help. Across ages, high neutralizing flu antibody responses were associated with robust Tfh1 activation, which was ICOS dependent in adults but not in children. Interestingly, Tfh depletion strategies revealed enhanced Tfh differentiation from distinct precursors in pediatric donors, yet antibody responses during early life were less reliant on Tfh help. Together, these findings define developmentally programmed differences in Tfh differentiation and function with implications for pediatric vaccine design.

immunology↗

bioRxiv2026

A tonsil organoid model reveals Epstein-Barr virus infected germinal center B cell states during primary infection

Epstein-Barr virus (EBV) colonizes secondary lymphoid tissues to establish persistent infection and is strongly associated with malignancy and autoimmunity. Our understanding of EBV infection biology is hindered by a lack of models that capture infected B cell activity in the lymphoid tissue microenvironment. We therefore developed an EBV human tonsil organoid model to evaluate key B cell states and antiviral responses, including after primary infection. EBV promoted B cell differentiation into germinal center (GC)-like phenotypes and transcriptomic analyses highlighted numerous B cell transcriptional programs unique to EBV-infected cells. B cell receptor repertoire analysis revealed that most EBV-infected B cells underwent class switching but only rarely participated in somatic hypermutation. CD4 T cells, highly activated by organoid infection, limited EBV+ B cell outgrowth. Our findings demonstrate human tonsil organoids as a physiologically relevant model to investigate key aspects of EBV immunity and pathogenesis.

immunology↗

bioRxiv2024

Tissue determinants of the human T cell receptor repertoire.

98% of T cells reside in tissues, yet nearly all human T cell analyses are performed from peripheral blood. We single-cell sequenced 5.7 million T cells from ten donors autologous blood and tonsils and sought to answer key questions about T cell receptor biology previously unanswerable by smaller-scale experiments. We identified distinct clonal expansions and distributions in blood compared to tonsils, with surprisingly low (1-7%) clonal sharing. These few shared clones exhibited divergent phenotypes across bodily sites. Analysis of antigen-specific CD8 T cells revealed location as a main determinant of frequency, phenotype, and immunodominance. Finally, diversity estimates from the tissue recalibrates current repertoire diversity estimates, and we provide a refined estimate of whole-body repertoire. Given the tissue-restricted nature of T cell phenotypes, functions, differentiation, and clonality revealed by this dataset, we conclude that tissue analyses are crucial for accurate repertoire analysis and monitoring changes after perturbing therapies.

immunology↗

bioRxiv2021

Loss of TDP-43 function and rimmed vacuoles persist after T cell depletion in a xenograft model of sporadic inclusion body myositis

Sporadic inclusion body myositis (IBM) is the most common acquired muscle disease in adults over age 50, yet it remains unclear whether the disease is primarily driven by T cell-mediated autoimmunity. IBM muscle biopsies exhibit nuclear clearance and cytoplasmic aggregation of TDP-43 in muscle cells, a pathologic finding observed initially in neurodegenerative disease, and nuclear loss of TDP-43 in neurons causes aberrant RNA splicing. Here, we show that loss of TDP-43 splicing repression, as determined by inclusion of cryptic exons, occurs in skeletal muscle of IBM patients. Out of 119 muscle biopsies tested, RT-PCR-mediated detection of cryptic exon expression is 84% sensitive and 99% specific for diagnosing IBM, indicating utility as a functional and diagnostic biomarker. To determine the role of T cells in pathogenesis, we generated a novel xenograft model by transplanting human IBM muscle into the hindlimb of immunodeficient mice. Xenografts from IBM patients display robust regeneration of human myofibers and recapitulate both inflammatory and degenerative features of the disease. Myofibers in IBM xenografts are invaded by human, oligoclonal CD8+ T cells and exhibit MHC-I upregulation, rimmed vacuoles, mitochondrial pathology, p62-positive inclusions, and nuclear clearance and cytoplasmic aggregation of TDP-43, resulting in expression of cryptic exons. Depletion of human T cells within IBM xenografts by treating mice intraperitoneally with anti-CD3 (OKT3) suppresses MHC-I upregulation, but rimmed vacuoles and loss of TDP-43 function persist. These data suggest that myofiber degeneration occurs independent of T cells, and muscle cell-intrinsic mechanisms, such as loss of TDP-43 splicing repression, drive IBM pathogenesis. One Sentence SummaryDepletion of T cells in a xenograft model of sporadic inclusion body myositis suppresses inflammation but not TDP-43 pathology or muscle degeneration.

pathology↗