https://media.hhmi.org/biointeractive/click/immunology_primer/01.html
Click the link above to access the Cells of the Immune System tutorial. 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. The link posted above describes key elements of
the adaptive immune system, including B cells and antibody molecules, helper T cells and cytotoxic T cells, and antigen presentation.
In facilitating your understanding in this tutorial from Howard Hughes Medical Institute (www.hhmi.org/biointeractive), a worksheet is provided for you to answer and then submit.