Accepts electrons from cytochrome c, ultimately transferring them to oxygen, forming H2O. in the process, 2 protons are pumped across the membrane. Complex IV is a terminal oxidoreductase, meaning that it transferes the elctrons to the terminal electron acceptor, which, in this case, is O2.
White blood cells called lymphocytes originate in the bone marrow but migrate to parts of the lymphatic system such as the lymph nodes, spleen, and thymus. There are two main types of lymphatic cells, T cells and B cells.
In some cases, pathogens are very resistant to adhesion by the macrophages. The antigen presentation on the surface of infected macrophages (in the context of MHC class II) in a lymph node stimulates TH1 (type 1 helper T cells) to proliferate (mainly due to IL-12 secretion from the macrophage).