This tutorial provides an overview of the immune system, concentrating on the roles played by B and T lymphocytes, and on the antigen-presentation system.

All animals possess a nonspecific defense system called the innate immune system, which includes macrophages in mammals. Vertebrates have an additional powerful immune response called adaptive immunity. This Click & Learn describes key elements of the adaptive immune system, including B cells and antibody molecules, helper T cells and cytotoxic T cells, and antigen presentation.

The accompanying worksheet guides students’ exploration.