IMMUNOMODULATOR - A relatively new class of monoclonal antibody medications that work by binding to a biochemical mediator known as tumor necrosis factor. Tumor necrosis factor is a chemical mediator that is involved in normal inflammatory and immune responses, typically seen in rheumatoid arthritis. Examples include etanercept (Enbrel), infliximab (Remicade), and leflunomide (Arava).