Chen and Lipschitz et al. used immunostaining and in situ hybridization to analyze large B cell lymphoma biopsies from patients treated with autologous CAR T cells expressing a second generation (CD3ζ and CD28) anti-CD19 scFv. PD-1+CD8+ T cells were increased in responsive patients’ specimens taken >5 days post infusion. CAR T cells were the minority of intratumoral T cells, and most CAR and non-CAR T cells expressed Ki67, IFNγ, granzyme B and/or PD-1, and markers of current/past activation. In biopsies with CAR T cells, activated non-CAR T and other immune cells were present at 5-10 fold higher levels and were the sole source of IL-6 in almost all samples.
Contributed by Paula Hochman
ABSTRACT: The mechanisms of CAR-T cell mediated anti-tumor immunity and toxicity remain poorly characterized due to few studies examining the intact tumor microenvironment (TME) following CAR T-cell infusion. Axicabtagene ciloleucel is an autologous anti-CD19 chimeric antigen receptor (CAR) T-cell therapy approved for patients with large B-cell lymphoma. We devised multiplex immunostaining and in-situ hybridization assays to interrogate CAR T cells and other immune cell infiltrates in biopsies of diffuse large B-cell lymphoma following axicabtagene ciloleucel infusion. We found a majority of intratumoral CAR T cells expressed markers of T-cell activation but, unexpectedly, comprised