Mucosal-Associated Invariant T Cells in T-Cell Non-Hodgkin Lymphomas: A Case Series

SIMPLE SUMMARY: Mucosal-associated invariant T (MAIT) cells are a subgroup of T lymphocytes whose role has recently been investigated in several types of diseases, including cancer. However, little is known about these cells in lymphomas. In this case series, we investigated the presence of MAIT cells in biopsies obtained from patients diagnosed with T-cell non-Hodgkin lymphomas, uncommon hematological malignancies with often not clearly defined etiopathology. ABSTRACT: Background: Mucosal-associated invariant T (MAIT) cells are a subset of unconventional T lymphocytes expressing a semi-invariant α/β T-cell receptor (TCR). The physiological functions of these cells, which are particularly abundant in normal liver and mucosal sites, have become clear only in recent years, but their role in most human diseases is still unknown. Since the cellular origin and etiopathogenesis of most T-lymphomas are still elusive, we decided to explore the presence of MAIT cells in biopsies from these neoplasms. Methods: Sixteen biopsies obtained from patients with a T-cell lymphoma diagnosis were analyzed via immunofluorescence staining using an anti-Vα7.2 antibody and the MR1-antigen tetramer. Positive cases were subjected to a polymerase chain reaction for the detection of Vα7.2–Jα33, Vα7.2–Jα20, or Vα7.2–Jα12 rearrangements, followed by sequencing of the CDR3α region. Results: CD3+/Vα7.2+ and CD3+/MR1-Ag-tetramer+ cells were found in 4 of 16 samples analyzed. The identification of specific TCR rearrangements confirmed the presence of these cells in all four samples. PCR and sequencing results documented the presence of multiple clones of MAIT cells in each positive sample. Conclusions: MAIT cells are frequently found in T-cell lymphomas. More in-depth studies and a larger number of samples are needed to better clarify the contribution of MAIT cells to this rare neoplasm.