Although the mechanism of action of LAG-3 is incompletely understood, its interaction with MHC class II causes downregulation of T cell cytokine production, CD4 and CD8 T cell expansion, and favors Treg phenotype adoption to prevent tissue damage and autoimmunity [17] T cells located in the TME, known as tumor-infiltrating lymphocytes (TILs), overexpress LAG-3 which results in cell dysfunction, immune exhaustion, and favorable conditions for tumor growth [18]. This evidence concerns the gene LAG3 and Autoimmunity.