The evolution of a system

Hsps are potent because some immune cells have specific docking sites for the hsps and, as Srivastava found in 1995, the cells’ intracellular pathways direct the attached peptides so that they are displayed to the rest of the immune system.

Presumably this complicated pathway has not evolved for the benefit of cancer immunologists. Rather it may be a primitive early warning system – the original signal that cells are under attack and dying. "It’s a bit like blood – if you see it on the floor something bad has happened," says Srivastava.

Dendritic cells bind hsps.

Hsps first evolved to deal with stresses (such as heat) inside single bacterial cells. Now those same hsps may have become an alert signal carried between cells of multicellular organisms. As the most abundant proteins inside cells, hsps are certainly well suited to the job. Plus they do their job (of folding proteins and protecting proteins from heat) by binding peptides. This same peptide-binding ability means that they can carry the proteins of invading infectious agents from cell to cell.

continue...

Vaccinating against cancer