Phenotypic and functional analysis of human Natural Killer lymphocytes in patients affected by haematological neoplasms treated with autologous T lymphocytes genetically modified with chimeric antigen-specific receptor

Chimeric antigen receptor T cell therapy represents a novel perspective for patients with aggressive, chemotherapy-refractory B cell neoplasms. While CAR-T cells exhibit direct cytotoxic properties, other immune populations may also contribute to treatment response and complications. Macrophages and dendritic cells are recognized as key-mediators of CAR-T cell associated inflammatory toxicities, while emerging evidence suggests that regulatory T cells may hamper CAR-T cell efficacy. To investigate NK cell dynamics, we performed peripheral blood flow cytometry in 40 patients before and after CAR-T cell therapy for diffuse large B cell lymphoma. Our analysis revealed that early NKG2A+ KIR⌐ NK cells repopulate shortly after CAR-T infusion. Within the CD56dim subset, NKp46+ NK cells frequencies progressively increased overtime, while NK cells expressing the inhibitory receptor Siglec-7 were abruptly depleted. PD-1 was already detectable before lymphodepletion and increased thereafter, potentially reflecting NK cell activation or glucocorticoid treatment to mitigate inflammatory complications. Higher PD-1 levels were associated with severe inflammatory complications. Patients who achieved a response to therapy exhibited enriched populations of NKp46+, CD62L+ NK cells, likely with lower proportions of PD-1+ circulating NK cells. Overall, our findings suggest that NK cells undergo dynamic changes following CAR-T cell therapy, potentially driven by lymphodepleting chemotherapy and cytokines release. Further studies are needed to clarify their role in inflammatory complications and treatment outcomes.