<qa>  What is a protein that can trigger the cells of the immune system to recognize, remember andSeveral such approaches have used dendritic cells DCs, which are known to be potent antigen presenting cells. An antigen is a protein that, when shown to the immune system in the right way, can trigger the cells of the immune system to recognize, remember and eliminate other cells that also display that specific antigen. The cancerous cells in tumors present antigens in such a way that the bodys immune system often fails to recognize and eliminate them. It is theorized that when DCs are fused to tumor cells the resulting fused cells will be capable of presenting tumor antigens in an enhanced manner, thus allowing the bodys immune system to recognize the tumor antigens on the cancer itself. If this occurs, the patients immune system may be specifically stimulated, producing a clinically meaningful immune response against the tumor. 