Immunobiology and conflicting roles of the human CD161 receptor in T cells

Human C‐type lectin‐like CD161 is a type‐II transmembrane protein expressed on the surface of various lymphocytes across innate and adaptive immune systems. CD161+ T cells displayed enhanced ability to produce cytokines and were shown to be enriched in the gut. Independently of function, CD161 was used as marker of innate‐like T cells and marker of IL‐17‐producing cells. The function of CD161 is still not fully understood. In T cells, CD161 was proposed to act as co‐signalling receptor that influence T‐cell receptor‐dependent responses. However, conflicting studies were published demonstrating lack of agreement over the role of CD161 during T‐cell activation. In this review, we outline phenotypical and functional consequences of CD161 expression in T cells. We provide critical discussion over the most pressing issues including in depth evaluation of the literature concerning CD161 putative co‐signalling properties.