Rheumatoid Arthritis (RA) is a chronic inflammatory disease which afflicts joints in particular and usually leads to joint destruction. Almost one percent of the world's population is afflicted. The disease can appear during any stage of life but usually starts during the fourth or fifth decade. Women are usually afflicted three times as often as men.

RA is an autoimmune disease. This means that the human immune system, which is supposed to contain pathogens such as bacteria, viruses and fungi, attacks its own organs due to erroneous programming.

What causes the immune system's erroneous programming and why the defense mechanism can no longer distinguish between "self" and "non-self" is not yet known in detail. However, we do know that the human organism - even a healthy one - repeatedly creates immune cells that turn against the body's own tissue. These "autoreactive" T cells are however immediately recognized and incapacitated by the intact immune system before they can do too much damage. Specialized immune cells, so-called regulatory T cells (Tregs) are responsible for this. Through direct contact with the cells they inhibit the autoreactive T cells and thus impede their attack on the body's own tissue.

This is different in patients with autoimmune diseases:

In this case, the Tregs are not fully functional for some as-yet-unknown reason. The autoreactive T cells are therefore not sufficiently suppressed. They can multiply to a large extent unhindered and attack and destroy the body's own tissue. One modern therapeutic strategy for autoimmune diseases as pursued by Biotest is therefore aimed at re-establishing the Tregs' functionality so that they are able to reassume their natural control function against autoreactive T cells (Biotherapeutic agent BT-061).