hundreds of millions of cells comprise the immune system and are distributed throughout the body in cells that circulate through the blood and lymph systems, whereas others reside in the primary (bone marrow and thymus) and secondary (spleen, lymph, gut, intestines) lymphoid tissues, the skin, and the mucosa of the respiratory, alimentary and genito-urinary tracts.
as you can see, immune cells are places all over the body, so it would seem they are at a disadvantage when it comes time to work together, seeming as they are so far apart. so the key to their success is to be able to communicate quickly and efficiently and that all cells can go where they are needed, and kick pathogen ass
molecules that help communication among immune cells are referred to as cytokines. they do the following three:
- the interaction of a cytokine with its receptor on a target cell can cause changes in the expression of adhesion molecules and chemokine receptors on the target membrane, thus allowing it to move from one location to another.
- cytokines can also signal an immune cell to increase or decrease the activity of a particular enzyme or change its transcriptional program, thereby altering and enhancing its effector functions.
- finally, they can instruct the cell when to survive or when to die with a process known as apoptosis--programmed cell death
early attempts classified cytokines as interleukins which basically meant they communicated between white blood cells (WBCs)
chemokines is like a subgroup of cytokines in the regard that chemokines are specific to the purpose of mobilizing immune cells from one organ, or indeed, from one part of an organ, to another.
chemokines belong to the class of molecules called chemoattractants, molecules that attract cells by influencing the assembly, disassembly, and contractility of cytoskeleton proteins and the expression of cell-surface adhesion molecules. chemokines attract cells with the appropriate chemokine receptors to regions where the chemokine concentration is highest.
chemokines, for example, are important in attracting cells of the innate immune system to the site of infection and inducing T cells to move toward antigen-presenting cells in the secondary lymphoid tissues.
cytokines communicate in three different types of ways, that really are distinguished by the distance of communication. they are the following:
Review Figure 4-1
- endocrine--acting on cells from a distance, thus need to travel through the blood stream/circulate to reach their target
- paracrine--cytokines that act on neighboring cells by simply diffusing molecules through tissue fluids or across an immunological synapse
- autocrine--occurs when a cell needs to promote a positive feedback loop by self stimulation.