It is still in the experimental stage for treating ITP, however initial results are encouraging. Clinical trials are in progress. Rituxan reduces the number of B cells in your body.
B cells are a type of white blood cell that, when activated, multiply and produce antibodies.
Since Rituxan reduces the number of B cells it reduces the number of cells that produce antibodies including the antibodies that attack platelets. Antibody production is triggered by antigens. An antigen and antibody fit together like a key in a lock. When an antigen and antibody key and lock are joined in a B cell the body eliminates it since that B cell's work is done. CD20 is the name of one antigen that is closely associated with B cells.