A molecular and cellular based approach to understanding the immune system by characterizing both the innate and adaptive immune systems and their functions. Emphasis is placed on the adaptive immune response, including humoral immunity and cell-mediated immunity, antigens and antigen recognition, immunoglobulins, B cell and T cell development, activation, and differentiation, and the effector functions of these different cells and branches of the immune system to create a comprehensive response to defend the body against pathogens. Other topics include immune system dysfunction (hypersensitivities, autoimmunity, and immunodeficiencies) as well as vaccine mechanisms. Not open to students with credit in BIOL 503. Prerequisite: BSCI 400, BIOL 400 or BIOL 401, or consent of instructor.