To understand how mycoplasma causes arthritis, it’s necessary to comprehend how the immune system responds to a mycoplasma infection.

Mycoplasma lacks a cell wall, and therefore has to live inside our own cells. (Most other infectious bacteria have their own cell walls, and therefore can live outside our cells.)

The immune system is well-equipped to deal with bacteria that have cell walls. When infected with such bacteria, the immune system sends white blood cells to the site of infection and releases toxic chemicals to kill the bacteria.

The process is very different with a non-cell wall bacteria because the immune system has no good way to treat an intracellular infection.

Cells infected with mycoplasma take on an irregular shape. The immune system recognizes that the infected cells are abnormal, but must use a different mechanism to fight the infection.

In this case, the immune system produces antibodies that attack our own cells in order to get rid of the infectious agent.

Unfortunately, this defense mechanism can go wrong if the antibodies begin to attack not only infected cells but healthy cells as well. When this occurs, it can lead to what’s called an autoimmune disease.