4.Bacterial growth and death of alveolar macrophages produce powerful chemotactic factors that cause a large influx of polymorphonuclear leukocytes and monocytes from the peripheral blood.
5.At the same time, the macrophages produce molecules called cytokines and chemokines that alert the rest of the immune system to the presence of the invader.
6.They initially circulate in the recipient's peripheral bloodstream, but molecules on the stem cells, called chemokines, act as homing devices and quickly traffic them back to the marrow.
7.Immune cells release various chemokines which creates an inflammatory reaction that makes epithelial cells secrete more mucus and makes the blood vessels in the walls of the airways more leaky.
8.The immune system responds to the antigen by flooding the subarachnoid space with white blood cells, which, release chemokines - and create inflammation and this results in the classic triad of symptoms: headaches, fevers, and neck stiffness.