GEOapplication/xmlftp://ftp.ncbi.nlm.nih.gov/geo/series/GSE337nnn/GSE337136/primaryOK200OtherHomo sapiensOtherhttps://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE337136GEOGSEfalseImmunophenotyping of peripheral CD8+ T cells from classical Hodgkin Lymphoma patients treated with PD-1 blockade [TCR-seq]The immune microenvironment of classical Hodgkin lymphoma (cHL) is characterized by rare Hodgkin–Reed–Sternberg cells surrounded by dysfunctional lymphocytes, with support from PD-1/PD-L1 interactions. Although PD-1 inhibitors (PD-1i) are effective in some relapsed cHL patients, the mechanisms of resistance remain unclear. We investigated T cell dynamics in cHL using whole-exome sequencing (WES) of plasma circulating tumor DNA and longitudinal single-cell RNA and T-cell receptor sequencing of peripheral blood lymphocytes from a relapsed patient before and after PD-1i therapy. Findings were validated at the protein level by flow cytometry in 11 relapsed HL patients (pre- and post-PD1i) and 6 healthy age-matched controls, and by PhenoCycler imaging of 24 tissue biopsies (13 diagnostic, 11 post-PD1i). WES identified two somatic mutations at relapse—MEX3B-Lys201* and TNFRSF10A-Tyr409His—potentially contributing to immune escape. Immune profiling revealed clonal expansion of CD8⁺ T cells at relapse and a shift from precursor-like (TCF1⁺) to intermediately exhausted (CX3CR1⁺) phenotypes. This pattern was confirmed in other relapsed cHL patients, in whom TCF1⁺ populations diminished, and CX3CR1⁺ T-bet⁺ populations became dominant among those progressing on PD-1 therapy. In tissue biopsies, post-PD1i-treatment CD8⁺ T cells exhibited increased levels of exhaustion markers (TCF1⁻, CX3CR1⁺), a phenotype not observed in diagnostic cHL or healthy donors. These results suggest that durable PD-1i responses depend on the preservation of progenitor-exhausted T cells, whereas relapse post PD1i is marked by the accumulation of intermediately exhausted clones. Strategies to prevent T cell exhaustion or combine PD-1 inhibition with approaches targeting antigen burden may help overcome resistance.2026/08/20GSE337136GSM9848699GSM9848700GSM9848698GSM9848701GSM984870215520337136Homo sapiens