Circulating mucosa-associated invariant T cells are decreased and have impaired function in patients with diffuse large B-cell lymphoma.

Mucosa-associated invariant T (MAIT) cells are associated with tumor immunity. However, their role in diffuse large B-cell lymphoma (DLBCL) remains unclear. Therefore, this study aimed to elucidate frequency and functional characteristics of circulating MAIT cells in DLBCL patients. The findings revealed a significant reduction in the frequency of circulating MAIT cells in DLBCL patients compared to age-matched healthy controls. Moreover, circulating MAIT cells from DLBCL patients exhibited proapoptotic and senescent phenotypes and demonstrated dysfunction, as evidenced by elevated expression of activation and exhaustion markers, including CD69, CD25, HLA-DR, PD-1, and Tim-3. MAIT cells derived from DLBCL produced lower levels of crucial anti-tumor cytokines, such as interferon-gamma, interleukin-17, tumor necrosis factor-α and granzyme B, suggesting impaired anti-tumor immunity. Additionally, MAIT cells from DLBCL patients showed diminished cytotoxicity against DLBCL cells compared to those from healthy donors. Notably, a lower frequency of circulating MAIT cells in patients with DLBCL was associated with poor prognosis. In summary, this study reveals reduced and impaired circulating MAIT cells in DLBCL patients, suggesting their importance in anti-lymphoma immunity.