Rituximab is a monoclonal antibody therapy that targets CD20, a protein found on the surface of B-lymphocytes, a type of white blood cell involved in the immune response. Rituximab is used in the treatment of various autoimmune diseases, such as rheumatoid arthritis, lupus, and multiple sclerosis, as well as certain types of cancer, such as non-Hodgkin's lymphoma and chronic lymphocytic leukemia. It works by binding to CD20 on B cells and causing their destruction, leading to a decrease in inflammation and immune response. Rituximab has shown promising results in clinical trials and is considered a valuable treatment option for patients with these conditions.