Mucosal-associated invariant T cells are depleted and functionally altered in patients with common variable immunodeficiency.

Common variable immunodeficiency (CVID) is a primary immunoglobulin deficiency characterized by recurrent infections and complications, including autoimmunity, enteropathy, polyclonal lymphocytic infiltration or lymphoid malignancy. Innate T cells can support B cell maturation and antibody production. We investigated the numbers, phenotypes and functions of circulating B cell, γδ T cell, invariant natural killer T (iNKT) cell and mucosal-associated invariant T (MAIT) cell subsets in 23 CVID patients and 27 healthy controls. Switched-memory B cells and plasmablasts were depleted in CVID patients (p<0.0001). γδ T cells were found at normal numbers, but iNKT and MAIT cells were depleted (p<0.0001 and p<0.002). MAIT cells were especially low in patients with complicated CVID (p<0.05). MAIT cells from patients appeared more activated and more frequently produced interleukin-17A, interleukin-22 and tumor necrosis factor-α than MAIT cells from healthy subjects in vitro. Thus, MAIT cell depletion and activation may contribute to immunodeficiency and complications associated with CVID.