This course is designed as an introduction to the immune system. Our goal is to understand the basic elements of the immune system and the mechanisms by which these elements protect us from infectious agents, growth of tumors and other pathologic conditions. The overview design of the course will not preclude us from exploring a few areas in depth and students will also have an opportunity to dig deeply into an area of their choosing when writing papers and doing group presentations. We will stress the experimental basis of each concept we discuss. This will enable us to see how scientists analyze questions, design experiments and draw conclusions. This process will show us how fluid "facts" are and how they are being continuously modified. Primarily for this reason, we stress understanding the process rather than memorizing the "fact". The rapid pace of discovery makes the study of the immune system exciting and challenging. This course will provide you with enough background to pursue further study in this area. Prerequisites: physiology, cell biology or molecular biology.