Much of cancer’s biological power comes from the fact that to the body, it doesn’t always seem like a pathogen.

Because cancer arises from mutations in each patient’s own DNA, the disease complicates our immune system’s central task of differentiating between body and foreign object,
host and invader,
“self” and “not self.”

Physicians long hypothesized that there was a link between cancer and swelling
—a critical sign that the immune system “sees” an enemy to ward off.

In the 1890s #William #Coley,
now known as the father of #immunotherapy,

successfully spurred remission in patients with inoperable tumors by injecting them with bacteria like those that cause strep throat.

But the mechanisms behind Coley’s treatments were poorly understood,
and for decades after his discovery, researchers weren’t sure our immune systems could detect cancer at all.

Because doctors didn’t know exactly how the body perceives and responds to cancer,
early treatments were highly invasive and highly toxic:

The first tactic was major surgery on the organs where cancer was taking root.

That was followed in the 20th century by the development of systemic radiation and chemotherapy to attack cancer cells throughout the body.

Over time oncologists narrowed and refined these approaches incrementally,
using more precise surgery,
more focused radiation
and chemo that killed fewer normal cells as collateral.

Still, the dream was to harness immunotherapy,
which represented a dramatic departure from the usual tactics in seeking to use the human body’s own systems to go after cancer in a more targeted way.

As demand for COVID vaccines has slackened,
there has been a rush to apply mRNA technology to a long list of illnesses.

The first real proof that immune cells are capable of recognizing tumors didn’t come until the 1950s and 1960s.

Gradually, researchers came to understand that cancer deploys a host of tricks to suppress the immune response to growing tumors.

Some forms of cancer use fibrous tissue called #stroma to construct shields that make it difficult for immune cells to penetrate or attack tumors.

Other cancers take advantage of the balancing act our immune systems are always performing when they decide how heavily to invest the body’s defenses in warding off a given threat.

Some tumors produce proteins that can shut down key immune cells.

Tumors may even recruit immune cells to promote the growth of blood vessels that will supply them with oxygen and nutrients.

As scientists learned more about how cancer manipulates the immune system,
they started identifying ways to thwart it.

Inside our cells, proteins are constantly being chopped up into smaller sequences of amino acids,
some of which are then presented on the cell surface as part of what’s collectively known as
the major histocompatibility complex, or #MHC
—essentially the immune system’s tool for differentiating self and foreign molecules.