Concept 43.1  Innate immunity provides broad defenses against infection	43.01
 Concept 43.2  In acquired immunity, lymphocytes provide specific defenses against infection	43.02
 Concept 43.3  Humoral and cell-mediated immunity defend against different types of threats	43.03
 Concept 43.4  The immune system's ability to distinguish self from nonself limits tissue transplantation	43.04
 Concept 43.5 Exaggerated, self-directed, or diminished immune responses can cause disease	43.05
Activity: Immune Responses	43&A
Activity: HIV Reproductive Cycle	43&B
Investigation: What Causes Infections in AIDS Patients?	43&A
Investigation: Why Do AIDS Rates Differ Across the U.S.?	43&B
Video: T Cell Receptors	TCellReceptors-V.html=TCellReceptors-V.swf