Editing Immunology (section)

== 3. Cellular Signaling: The Language of Immunity ==

The innate and adaptive systems do not operate in isolation; they are deeply integrated through complex cellular signaling.

* '''Cytokines:''' A broad category of small proteins secreted by immune cells that affect the behavior of other cells around them. They regulate the intensity and duration of the immune response. 
* '''Chemokines:''' A specific type of cytokine that acts as a chemical beacon, guiding circulating white blood cells directly to the site of infection or tissue damage.
* '''Antigen Presentation:''' The critical bridge between the two systems. After a macrophage or dendritic cell digests a pathogen, it displays fragments of the pathogen's proteins (antigens) on its surface using a structure called the Major Histocompatibility Complex (MHC). It physically travels to the lymph nodes to "present" these antigens to T cells, officially initiating the adaptive response.