ANTIGEN-MHC COMPLEX
Cell-mediated immunity is most effective against cells infected by a virus. It also is effective in the elimination of host cells that have become cancerous. Although the response to the antigen differs between antibody-mediated and cell-mediated immunity, the beginning sequence of steps is similar for both. Antigens detected by macrophages and other antigen-presenting cells, such as dendritic cells, are ingested and broken down. The breakdown products are then joined with molecules referred to as major histocompatability complex (MHC) proteins. The antigen-MHC complex is then exposed on the surface of the antigen-presenting cell.