Even veteran HIVers sometimes get all those different kinds of white blood cells mixed up. Here’s help for the bloodhound:
Lymphocytes—Xenophobic white blood cells responsible for booting from the body anything foreign (viruses, bacteria, even tumors). Lymphocytes include T cells (see below), B cells (Bs make antibodies, proteins that destroy interlopers) and the rare NK (“natural killer”) cells, which target virus-infected or cancerous cells.
T Cells—A type of lymphocyte, they’re “T” cells because they’re programmed in the thymus gland (in your neck). Ts discriminate between friend (your own body or immune system) and foe (anything alien). They fall into two groups: CD8+ T cells (which fight infection within cells) and the studly, drill sergeant CD4+ T cells (which tell the Bs to make those antibodies).
CD4+ Cells—Pronounced “cee dee four positive.” When docs say “Your T-cell count is...,” they really mean “Your CD4+ T-cell count is....” Generally called “T helper cells,” these brave little units are specifically targeted by HIV. Doctors count ’em to determine the overall strength of your immune system.