There are many different types of immune system cells. The general categories you should be familiar with are 1. Antigen-presenting cells 2. B lymphocytes and 3. Immunological specificity and memory involve formation of antigen-specific receptors during development, recognition of antigen, repeated cell divisions that produce clones of lymphocytes, and lymphocyte differentiation into effector and memory populations.
Memory cells are the basis of immunological memory.
Compared with the primary immune response, the secondary response is faster, longer, and stronger. This aspect of immune system biology is the basis of immunization. Read Sections 40.1, 40.2, 40.3, 40.4, 40.5, 40.6, 40.7, 40.9, and 40.10. Tables 40.1, 40.2, and 40.4 provide extremely useful summaries. The remarkable capacity of the immune system to respond to many thousands of different substances with exquisite specificity saves us all from certain death by infection.