202211201922
Status:
Tags: Immunology

CNS Immune System

• The main immune cells in the brain are microglia and astrocytes
  • Microglia have phagocytic functions
  • Infiltration of macrophages & activated T cells also possible

Routes of bi-directional communication

• HPA axis activity leads to release of Cortisol, and recruitment of immune cells through CORT binding to GRs on immune cells.
• Autonomic nervous system releases noradrenaline (norepinephrine), ACh, and adrenaline, all of which immune cells have receptors for
• Brain releases neuropeptides CRH, substance P, and endorphins which can enter the blood stream. White blood cells have receptors for these which are related to regulation & fine-tuning of immune response.

Indirect humoral pathway

• Cytokines released by white blood cells can enter brain or stimulate perivascular tissue which can produce cytokines or other anti-inflammatory agents themselves.

Direct neural pathway

Vagus nerve senses presence of cytokines by activated cells, propagating signal to nucleus tractus oslitarius which gives signal in the brain → behavioral changes

Direct humoral pathway

Cytokines can cross the BBB or enter brain through active transport mechanisms, which can happen in cases of infection, injury, chronic inflammation (e.g. Multiple Sclerosis)