Because the down-regulation of MHC class I activity in cancer is known to decrease the expression of tumor-associated antigen (TAA) and prevent cytotoxic T-cells (CTLs) from recognizing and destroying tumors [18], it is postulated that low expression levels of the MHC class may contribute to tumor development, as suggested previously in in vivo immune-tumor interaction [25]. The gene discussed is HLA-C; the disease is cancer.