Killer T cells launch an aggressive attack but don't last for long. Scientists are working on ways to draw a few back to a subdued memory form.
It does well to remember your enemies. When the human body encounters an infectious agent for the first time, it (often) successfully beats back the intruder by expanding in great number the immune cells that are specially equipped to clear out the pathogens and infected cells. After health is restored, a few "memory" versions of these immune cells remain, such that, should the infectious agent make a second unwelcome appearance, the immune response is quicker and more intense.The same is true for cancer. Scientists more than ever are appreciating the role the immune system plays in responding to malignancies. A well-functioning immune system eliminates burgeoning tumors, but cancer finds ways to evade immune cells or to trick them into leaving it alone. Here as well, immunological memory is important: If cancer returns after an initial treatment, we want the immune cells to be ready for a Round 2.
So the name of the game in cancer immunotherapy is persistence. Although much effort has been put into developing the brutal soldiers of the immune system -- using what are called killer T cells -- these soldiers don't last for long. Just like a set of memory cells are useful to repel an infection for the second time, perhaps when it comes to cancer immunotherapy a treatment is in order that can transition some of the killer T cells into ones with more of a memory, long-lasting, attribute.
One lab has found that vitamin D may be just what the doctor ordered. This vitamin was determined to induce a broad immune memory pool. A new project will set out to discover whether vitamin D is useful during the time of a vaccination or immune treatment, and whether long-term administration of vitamin D is needed.
Another group reports that regulatory T cells, or Tregs, assist in creating memory cells. Tregs put the brakes on the immune system, helping to prevent autoimmune disorders, but evidence suggests that Tregs are also exploited by pathogens and cancers to evade immune surveillance. Understandably, Tregs tend to be thought of as unwitting allies of cancer, but this study suggests that Tregs are useful for reining back killer T cells before they all go out in a blaze of glory, preserving some of them to fight another day.
2. Kalia, V et al. Quiescence of memory CD8+ T cells is mediated by regulatory T cells through inhibitory receptor CTLA-4. Immunity 2015;42(6):1116-29.