Final answer:
Microglia and astrocytes are the primary responders to CNS injury, with microglia polarizing into M1 and M2 phenotypes that contribute to damage or repair, respectively. Reactive astrocytes are crucial for healing, accumulating at the lesion center. Molecules like ICAM-1 help leukocytes infiltrate the CNS, which, through releasing pro-inflammatory cytokines, can exacerbate neuronal damage.
Step-by-step explanation:
The primary responders to injury in the central nervous system (CNS) are microglia and astrocytes. Resting microglia can be polarized into M1 and M2 phenotypes. The M1 microglia contribute to neuronal damage by releasing cytotoxic factors like TNF-alpha, which are involved in pro-inflammatory responses. Conversely, M2 microglia play a role in CNS recovery by inducing Th2 anti-inflammatory responses and contributing to tissue repair and regeneration. Following injury, reactive astrocytes accumulate at the lesion center and release various mediators, including anti-inflammatory factors, that are crucial for the healing process. These reactive astrocytes and microglia are pivotal in the regulation of the CNS's immune response. Leukocytes can infiltrate the CNS during an immune response, facilitated by molecules such as ICAM-1, VCAM-1, P-selectin, and E-selectin on endothelial cells. The infiltration of leukocytes and the subsequent release of pro-inflammatory cytokines can lead to increased neuronal damage, further complicating the CNS injury response.