Through lecture, reading, and discussion, this course will help students understand the origin of immune cells in bone marrow development, the distinction between innate and adaptive immunity, and the function of the immune system in health and disease. The mechanisms responsible for the exquisite specificity of the adaptive immune system will be described. Throughout the course, the probable paths of evolution of the immune system will be stressed. As examples of major genetic diseases of immunity, case studies will be discussed on a weekly basis.