Mucosal-associated invariant T (MAIT) cells are innate-like T cells that recognize microbial infection via vitamin metabolites. The discovery of MAIT cells in the past two decades and the recent discovery of MR1 ligands has opened a new field and potential area for cellular immunotherapy using these unique cells. Their evolutionary conservation in mammals underscore their biological role in the host. In the past two years, we have been involved in the generation of MR1 tetramers as a tool for identification of these cells. Many groups have studied the role of these cells in clinical diseases.Here, we provide an up-to-date comprehensive review of clinical disease that have been studied with regards to MAIT cells.Original articles and review articles under the topic of MAIT cells and their relation to clinical diseases, both in human and animal models were included in the review.MAIT cells are potential candidates for future cellular immunotherapy. However, more understanding of the biological role of MAIT cells need to be elucidated first.