Mapping CD4+ T Cell Landscapes in Glioblastoma Reveals Effectors and Bystanders

Abstract

The tumor immune microenvironment (TME) has been demonstrated to significantly shape glioblastoma (GBM) progression and therapeutic response, yet the role of CD4+ T cells remains incompletely defined. Here, by integrating single-cell RNA, surface-protein, and TCR profiling of 39,788 T cells from 16 high-grade gliomas with five matched blood samples, we mapped 23,550 CD4+ T cells across 11 states and revealed predominance of CD4+ T cells in primary, but not recurrent, tumors, alongside pronounced tumor-blood discordance. Clonal analyses revealed expansion of cytotoxic effector CD4+ T cells within tumors and TEMRA CD4+ T cells in blood. A small set of dominant clonotypes (0.2% of unique TCR{beta} sequences) accounted for >6% of all CD4+ T cells across both compartments and were shared across different transcriptional subsets, suggesting diverse transcriptional development stemming from a shared progenitor. In contrast, virally annotated clonotypes were broadly dispersed and largely unexpanded, consistent with bystander populations. Collectively, we investigated the cellular and clonal architecture of human CD4+ T cells in GBM and highlight the contrast between PBMC and TIL compartments.