ABSTRACT
This chapter addresses the proposal that haematogenous cells are active participants in the initiation and repair of inflammatory insults in the central nervous system (CNS). To illustrate the involvement of haematogenous cells in CNS injury, it focuses on the contribution of the three main classes of leucocytes, namely, neutrophils to cerebral ischaemia and stroke, macrophages to wound healing and acute tissue injury, and lymphocytes to demyelination. Neutrophils accumulate in experimentally induced ischaemic regions of the brain and there is a strong correlation between the number of infiltrating neutrophils and the extent of ischaemic brain injury. In terms of functional activities, macrophages are probably the most versatile effector cells of the immune system. They are phagocytic, present antigen to T lymphocytes, and, upon activation, effect intracellular killing of pathogens and lysis of tumour cells. Unravelling the contribution of T lymphocytes to the demyelinating process has benefited from the study of the animal model of multiple sclerosis: experimental allergic encephalomyelitis.
