Talk about white blood cells.

True cells having a nucleus and organelles, devoid of Hb and plasma membrane contains proteins (histocompatibility antigens MHC, HLA antigens) serving as a basis for transplant acceptance. Leukocytes participate in immune and inflammatory reactions developed by organisms to protect itself form pathogenic agents (viruses, parasites...) involved in pathological immune reactions (hypersensitivity and autoimmune diseases) carried by blood and leave by diapedesis infiltration between endothelia, lifespan is few days (except memory T and B) 2 main categories: Granulocytes and Agranulocytes.