The Role of B and T Cells in Cancer Immunotherapy

Innate immune cells are tuned to recognize the usual suspects the bacteria, viruses, fungi, and parasites that evolved right alongside us and account for most of what needs defending against, Where there’s one invader there are probably more, so the cells of the innate immune system can also call for local reinforcements.

The call for help is chemical, in the form of the hormone-like proteins called cytokines. Many cytokines are like a distress beacon, with limited range and longevity, to prevent overreaction. There are many different flavors of cytokines, conveying many different messages. Each begins a complex choreography of chain-reaction defense responses within the body.

The result is a surprisingly sophisticated chemical communication that can call for more blood supply and tell the small blood vesicles (capillaries) to become more leaky, so fluid and reinforcements can flood in between the gaps (what we know as inflamma-tion), and even stimulate the local nerves to send out extra ouch! signals (so you pay more attention to the problem—and maybe remember not to do it again).

But more recently evolved critters on the tree of life-vertebrates with jaws, like us —also have an additional type of immune ármy, one capable of adapting to meet new challengers. This is the “adaptive” immune system, and it is able to face, fight, and remember unusual suspects: invaders that the body has never encountered before.

The major players of this adaptive immune system are two distinct types of cells that travel our bloodstream, with distinct tools of defense.’ These are the Band T Cells.

Diseases evolve and adapt. Nature invents new ones all the time. The B and T cells are part of a system that adapts to counter them. In terms of attacking cancer specifically, it’s the T cells we care about. But both B and T cells play a role in the cancer immunotherapy story.

Vaccines are the most successful form of immunotherapy, one we’ve been familiar with for hundreds of years. Their biological mechanism is dependent on the adaptive immune system. Vaccines train the cells of the immune system on a harmless sample of a disease that it might encounter later. The introduction allows the immune system to build up forces against anything that looks like that sample. Then later, if the live disease does show up, an immune army will be waiting for it?

Both B and T cells are involved with creating immunity. B cells were discovered first, so they get first billing. Before these immune cells migrate into our bloodstream, they mature from stem cells in the marrow of our bones. B cells* have a unique method of defending us against the stuff that causes disease. They don’t kill disease cells directly. Rather, they are factories that spit out antibodies —sticky, Y-shaped molecules that grab and hold on to foreign or non-self cells, and mark them for death.

Antibodies were originally called antitoxins, because they were assumed to be the stuff in blood that neutralized toxins—little customized antidotes that matched the poisonous molecules of disease like a lock to a key, canceling them out one by one.

B cells (and T cells) need to be ready to recognize anything that is non-self. This is possible because non-self, foreign, or diseased cells look different from normal body cells, at least to the discerning immune system. The difference is superficial; the outside of the cell is different. Foreign or sick cells have foreign proteins on their surface. The molecular marking is a distinctive bad cell fingerprint. These telltale fingerprint arrangements of foreign proteins on the surface of non-self cells are called antigens.

B cells create antibodies capable of recognizing the antigen fingerprints for even unknowable threats through an ingenious random genetic mix-and-match process that allows for 100 million different antibody variations. This variety is enough to ensure that at least one will match up with one of the many millions of possible protein arrangements of a foreign antigen. Every B cell makes antibodies to fit a randomly assigned antigen type. It’s something like a lottery ticket approach to recognizing random strangers. Every potential combination is covered by one or another of the B cells. It really only takes one antibody recognizing a foreign antigen to kick off the immune response.

Source : The Breakthrough: Immunotherapy and the Race to Cure Cancer by Charles Graeber

Goodreads : https://www.goodreads.com/book/show/39088907-the-breakthrough

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