E‐POSTERS

The adaptive immune response, and especially the role of T-cells has become a key focus in the treatment of lymphoma. The T-cell receptor (TCR) is exclusive for every T-cell clone and thus provides unique information about the condition of the immune system. Novel NGS sequencing has made it possible to identify hundred thousands of T-cell clones in a single sample, consequently termed the TCR repertoire. Poorer diversity of the TCR repertoire has been associated with inferior outcomes in other cancers [Thommen DS et al. -Cancer Cell 2018]. We explored how the systemic T-cell diversity impacted the long-term outcomes in lymphoma patients undergoing high-dose chemotherapy and autologous stem cell transplantation (ASCT). We performed high-throughput RNA based sequencing of the V, D and J segment of TCR beta chain with the Illumina Immune Repertoire NGS panel. In 288 patients with aggressive lymphoma (predominantly B-cell NHL), we have sequenced the circulating TCR repertoire in the autologous harvest products used in the ASCT. All patients were included in a nationwide Danish cohort with full longterm follow-up data on survival, infections, transfusion history and secondary cancers [Husby S et al. -Leukemia 2020]. By using the MiXCR and Immunarch bioinformatic pipelines we analyzed the TCR repertoire diversity, as measured by the Chao1 estimation, and used