MICA, a 383-amino-acid protein, interacts with the NKG2D receptor and the T cell receptor (TCR) to stimulate the activation of natural killer (NK) cells, αβ CD8 T cells, and γδ T cells. Typically undetectable in most cells, MICA is frequently found in epithelial tumors and its expression can be triggered by both bacterial and viral infections. The interaction between MICA and NKG2D leads to the activation of cytolytic functions and cytokine production in these effector cells, playing a crucial role in tumor surveillance, defense against viral infections, and the modulation of autoimmune responses.