Major structures of the immune system?

Organs of the immune system:

- Bone Marrow

- Thymus

- Spleen

- Lymph nodes

- Peyer's patches (in the small intestine)

- Appendix

- Tonsils

- Adenoids

Cells of the immune system:

- White blood cells (leukocytes)

- Neutrophils

- Eosinophils

- Basophils

- Lymphocytes (T cells, B cells, and NK cells)

- Monocytes

- Macrophages

- Dendritic cells

- Mast cells

- Natural killer (NK) cells