Recruited inflammatory cells - Introduction
You have just finished learning about the tissue resident cells and now we will introduce cells that are recruited into the tissue from the blood to help eliminate pathogens. These inflammatory cells include neutrophils, eosinophils and basophils that are all equipped with granules packed with molecules ready to be fired at the invading pathogen. These granulocytes will be individually presented in a bit more detail here. But there are also other innate immune cells that are recruited into the inflamed tissue, for example NK cells and a different type of innate T cell, called a natural killer T cell, or NKT cell. The NK cell is specialised in recognising and killing cells that have had a "personality change" either due to being infected by a virus or changed into a tumour cell. NKT cells on the other hand are cells that secrete many different types of cytokines and thereby bridge the innate and adaptive immunity.
So how do the inflammatory cells get from the blood to the site of injury or inflammation? These three videos together illustrate this process that is called transmigration and that also heavily involves endothelial cells of the blood vessel wall. Take a look at them in the order 1-3. Can you explain why inflammatory cells: 1) slow down, a process called rolling; 2) stop, a process called tethering; and 3) move towards the infection which is called chemotaxis?