CD4 and neoplasm: Although both classes share the task of presenting peptides on the cell surface for recognition by T cells, MHC I present peptides on nucleated cells and are recognized by cytotoxic CD8+ T cells, while MHC-II present peptides on antigen presenting cells (APC), including dendritic cells, macrophages, or B cells, and activate CD4+ T cells.20 Presentation of tumor antigens by APC through MHC-II to naïve T cells, by binding to T-cell receptor (TCR) and CD4, induces their activation.