HLA-DOA corresponding to MHC class II specifically presents antigens to T-helper cells (CD4+ T cells), and recent data suggested the importance of MHC class II in antitumor activity19,20, as CD4+ T cells can kill tumors both by directly binding to MHC II-expressing tumor cells and indirectly by activating tumor-infiltrating macrophages. The gene discussed is CD4; the disease is neoplasm.