In a process still imperfectly understood, HIV infects the CD4 cells (also called T4 or T-helper cells) of the body's immune system, cells that are necessary to activate B-lymphocytes and induce the production of antibodies (immunity). Although the body fights back, producing billions of lymphocytes daily to fight the billions of copies of the virus, the immune system is eventually overwhelmed, and the body is left vulnerable to opportunistic infections and cancers.
The principal parts of the immune system are the bone marrow, thymus, lymphatic system, tonsils, and spleen. the lymph nodes, tonsils, and spleen act to trap and destroy antigens from the lymph, air, and blood, respectively. Antigens are molecules that the body reacts to by producing antibodies, highly specific proteins also known as immunoglobulins. Antigens include bacteria and their toxins, viruses, malignant cells, and foreign tissues. Their destruction is accomplished by white blood cells (lymphocytes and the granulocytes and monocytes mentioned above), which are produced and constantly replenished by the stem cells of the bone marrow. The two types of lymphocytes are called B lymphocytes (B cells) and T lymphocytes (T cells). B cells are responsible for production of antibodies in what is called "humoral" immunity after the ancient medical concept of the body humors.
To educate your child or teen or just someone you know check out this website; it is full of helpful ways to educate your children, teen, or friend about this topic.