The immune system is broadly divided into innate and adaptive responses. The immune system uses a diverse army of signaling molecules called cytokines and chemokines to communicate among its distinct cell types, as well as with the nervous and endocrine systems.

The brain was once thought to be completely separate from the immune system, but we now know that it has its own resident immune cells- microglia- and likely is more exposed to peripheral immune cells than originally… Innate responses are rapid, non-specific, and stereotyped, meaning that they occur in more or less the same pattern and intensity each time a pathogen or antigen is encountered.

immune system — broadly divided into innate and adaptive responses.