Tetanus Toxoid is a vaccine made from inactivated tetanus toxin. It stimulates the immune system to produce antibodies against tetanus. In this trial, it is used as a booster vaccination to activate specific immune cells (B cells) and study how they respond in people with autoimmune diseases compared to healthy individuals. This helps researchers understand how the immune system works differently in people with autoimmune conditions.

Systemic sclerosis – A chronic autoimmune disease that causes hardening and tightening of the skin and connective tissues. It begins with inflammation and gradually leads to the buildup of scar tissue in the skin and various organs. The condition typically starts with skin changes in the fingers, hands, and face, and may progress to affect internal organs. The disease causes the immune system to attack the body’s own tissues, leading to tissue damage and fibrosis.

Systemic lupus erythematosus – A complex autoimmune disease where the immune system attacks various parts of the body, causing widespread inflammation. The condition can affect multiple organs and body systems, including the skin, joints, kidneys, and blood vessels. Symptoms often come and go in periods called flares and remissions. The disease commonly causes joint pain, skin rashes, and fatigue.

Rheumatoid arthritis – A chronic inflammatory disorder that primarily affects the joints, causing pain, stiffness, and swelling. The condition typically starts in smaller joints like fingers and toes, often affecting the same joints on both sides of the body. Over time, the persistent inflammation can lead to joint deformity and damage to the surrounding tissues. The disease occurs when the immune system mistakenly attacks the joint linings called synovium.