GEOapplication/xmlftp://ftp.ncbi.nlm.nih.gov/geo/series/GSE315nnn/GSE315929/primaryOK200OtherHomo sapiensOtherhttps://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE315929GEOGSEfalseDifferential T cell clonal dynamics underlie outcomes to frontline chemoimmunotherapy in advanced gastric cancer [TCR-seq]The addition of aPD1 to 5-FU/platinum in advanced gastric cancer (GC) yields variable responses. To understand cooperativity between chemotherapy and immunotherapy, we previously reported a phase II trial sequentially adding pembrolizumab to 5-FU/platinum. In this study, we use single-cell RNA- and TCR-sequencing to analyze 66,813 T cells from primary tumor biopsies pre-treatment, post-chemotherapy, and post-immunotherapy in 33 patients. We observed greater abundance, persistence, and recruitment of T cells with predicted tumor-reactivity in patients with prolonged progression-free survival (slow progressors). Increased B cell abundance and predicted B cell to T cell interactions supported T cell memory and co-stimulation, providing a mechanism for increased abundance and persistence of progenitor-exhausted and tumor-reactive T cells in slow progressors. T cell clones emerging in the tumor after immunotherapy were in the blood before treatment only in slow progressors. Our study thus highlights pre-treatment and early chemotherapy-induced T cell dynamics and B cell to T cell interactions that may drive durable response to chemoimmunotherapy in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 sapiens