Misbehaving “Killer” Cells Accelerate Progress of Autoimmune Disease

June 29, 2018

In 1998, scientists studying rheumatoid arthritis observed a population of immune cells that weren’t behaving the way they were supposed to. Immunologists noted the strange phenomenon, but decided not to pursue the subject further, and the cells were soon forgotten.

But interest in these cells has swelled over the past few years as they’ve been found in patients with chronic viral infections and cancer.

Now a new study, led by Quantitative and Systems Biology graduate student Kristen Valentine and UC Merced Professor Katrina Hoyer, published in The Journal of Immunology shows that these cells play a major role in autoimmune disease.

“Autoimmune disease is when your immune cells — whose job is to fight infections such as viruses, bacteria, fungal infections and things like that — make a mistake and instead target your own cells for destruction,” Valentine explained. “The immune system does all the same things it normally does in response to an invading pathogen, but with your own body as the target.”

Valentine and Hoyer were studying autoimmune diseases in mice when they found CD8 T cells — similar to those first identified in 1998 — popping up in strange places in mice with autoimmune hemolytic anemia (AIHA), a disease where the immune system targets healthy red blood cells for destruction.

CD8 T cells are the immune system’s “killers” – so named because they slay pathogen-infected cells to prevent the pathogen from spreading. CD8 T cells and other types of immune cells are supposed to hang out in separate areas of the lymph nodes, but Hoyer said some killer cells were “misbehaving.”

“We noticed that some CD8 T cells were moving into an area where they had not been seen before,” she said.

The killer cells were spotted in areas of the lymph nodes usually reserved for B cells — immune cells that produce antibodies, special proteins that engulf invading pathogens and tell other immune cells to destroy invaders.

Even stranger, the killers that had infiltrated the B cell region weren’t behaving like killers. They were acting like “helpers.”