GEOapplication/xmlftp://ftp.ncbi.nlm.nih.gov/geo/series/GSE345nnn/GSE345888/primaryOK200OtherHomo sapiensOtherhttps://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE345888GEOGSEfalseCellular and molecular mechanisms determining allogeneic CAR T cell rejection and expansion -- Submission 1 of 2 (Bulk TCR)Allogeneic CAR T cells could overcome limitations of autologous therapies but are limited by immune rejection. We evaluated 11 patients with large B-cell lymphoma treated with a single lot of cemacabtagene ansegedleucel (cema-cel), an allogeneic anti-CD19 CAR T product. Despite receiving identical infusion products, patients exhibited heterogeneous cema-cel expansion and clinical outcomes. Our integrated analyses using longitudinal TCRβ sequencing, single-cell molecular profiling, and mixed lymphocyte reaction assays revealed that high frequencies of pre-existing, recipient-derived alloreactive CD8+ T cells mediated rapid CAR T rejection in non-expanders. Furthermore, effector-like features, rather than stem/central memory programs, drove robust clonal CAR T expansion consistently across expanders. We confirmed similar expansion patterns in two independent cohorts treated with a separate lot of cema-cel or an allogeneic anti-BCMA CAR T product. These findings highlight distinct cell-extrinsic and cell-intrinsic mechanisms that influence allogeneic CAR T performance and provide insights to optimize donor selection, manufacturing, and product design.2026/09/23GSE345888GSM10018568GSM10018601GSM10018569GSM10018602GSM10018575GSM10018576GSM10018577GSM10018578GSM10018571GSM10018572GSM10018573GSM10018574GSM10018570GSM10018539GSM10018579GSM10018537GSM10018538GSM10018586GSM10018542GSM10018543GSM10018587GSM10018588GSM10018544GSM10018589GSM10018545GSM10018582GSM10018583GSM10018540GSM10018584GSM10018585GSM10018541GSM10018580GSM10018581GSM10018546GSM10018547GSM10018548GSM10018549GSM10018597GSM10018553GSM10018554GSM10018598GSM10018599GSM10018555GSM10018556GSM10018593GSM10018594GSM10018550GSM10018551GSM10018595GSM10018596GSM10018552GSM10018590GSM10018591GSM10018592GSM10018557GSM10018558GSM10018559GSM10018564GSM10018565GSM10018566GSM10018600GSM10018567GSM10018560GSM10018561GSM10018562GSM100185633017324676345888Homo sapiens[42788887]