Pathogens and Hosts Defense A is a multidisciplinary theme, involving faculty from the Departments of Microbiology and Immunology, Pathology/Laboratory Medicine, Medicine, Pediatrics, and Dermatology, as well as invited lecturers and volunteer faculty from the community. The fall semester introduces the basic concepts of molecular and medical microbiology and modern basic immunology, with emphasis on the application of those concepts to the understanding of human diseases. Lectures on selected topics in clinical immunology and infectious diseases are integrated with a variety of small group activities designed to stimulate the development of clinical problem-solving and self-education skills. Topics covered in the fall semester include fundamentals of bacterial physiology, growth and virulence, adaptive and innate immunity, mechanisms of hypersensitivity, tolerance and autoimmunity, and immunodeficiency. Major species of bacteria, fungi, and viruses pathogenic to humans are introduced in a clinical context. The mechanisms of action, side effects and clinical use of antimicrobial agents are introduced in the fall and reviewed in the spring