This unit includes a cut out puzzle with which the students can simulate an antibody-mediated and a cell mediated immune response. The unit describes how the immune system functions and how the HIV virus effects the immune system. The unit gives a description of common human diseases and describes how the immune system responds when attacked by bacteria, virus and cancer cells. The exercises in this unit include viewing short videotapes and answering questions about the immune system, a personal immunization record evaluation, and an antibody-mediated and cell mediated immune response. The unit concludes with a set of summary laboratory questions emphasizing the main concepts of the unit.