The immune system - master snooper

Vaccines are not limited to recognizing antigens on the surface of cells. In all cells, intracellular proteins are processed into peptides and translocated to the surface in Class I MHC molecules which are then recognized by antigen-specific receptors on T cells. If provided with the right stimulation at the same time that they are recognizing an antigen in the Class I MHC complex, these cells can go on to become cytotoxic T lymphocytes (CTLs) that go around killing cells expressing the antigen. In this way the immune system is always checking up on the identity of your body's cells and taking lethal action when appropriate. Creepy, isn't it?

This becomes important for efforts to develop vaccines to intracellular proteins such as p53. A study at AACR The particular study by Chikamatsu et al. claims that the presentation of wild-type (nonmutated) p53 peptides is enhanced in some tumors, providing a rationale for making vaccines against wild-type p53. The authors found several peptides from p53 that could elicit CTL activation in vitro when presented by dendritic cells, and these CTLs showed cytolytic activity toward squamous cell carcinoma of the head and neck cells in vitro. It remains to be seen how well this would work in the in vivo background of lots of cells expressing p53. Previous studies had proposed generating immune responses to particular mutant sequences of p53 commonly occurring in cancers.