Organs and Cells of the Immune System
- Bone Marrow
- Lymph Nodes
- T-Cells: There are two subsets of T-cells: CD4 cells and CD8 cells. CD4 cells secrete factors that activate other white blood cells that participate in the immune response. HIV attacks CD4 cells, damaging the body's ability to initiate the immune response. CD8 cells are important in directly killing tumor cells, viral infected cells and some parasites.
All the specialized cells of the immune system are formed in the bone marrow, where they mature. When they are fully mature they move into the blood stream where they do their work.
This small but important organ is where lymphocyte precursors become thymocytes, which in turn mature into T-cells. In addition, the thymus actually chooses which T-cells are best suited for the immune system. The remaining ones are eliminated by the body, assuring a healthy, effective immunity.
You can think of the spleen as a filter for the blood. It catches foreign material in the blood and activates different types of immune system cells.
The lymph nodes filter foreign material from the lymph fluid. Fluid that drains from various tissues in the body collects in the lymph system and passes through the nodes, being filtered as it passes.