When you're sick, you may wonder, "Why me?" But the real question should be, "Why am I not sick all the time?" You might even ask, "Why does my body respond with a fever, and is it really a good idea to lower it?" This course explores immunology, how the body defends itself from constant assault by parasites and pathogens. This course will present the fundamentals of both innate and adaptive immunity, emphasizing functional interactions among cells and organs. We will cover signaling, pathogen recognition and the division of labor among myeloid, lymphoid and supporting cells. The subject matter will also supply health professionals and biomedical researchers with the basic vocabulary and concepts necessary to understand both clinical press releases and primary literature. The course materials also provide support to other immunology instructors by presenting difficult concepts in creative ways using analogies and models.