Immune and inflammatory responses to stroke: good or bad?

P. A. McCombe, S. J. Read

Inflammatory and immune responses play important roles following ischaemic stroke. Inflammatory responses contribute to damage and also contribute to repair. Injury to tissue triggers an immune response. This is initiated through activation of the innate immune system. In stroke there is microglial activation. This is followed by an influx of lymphocytes and macrophages into the brain, triggered by production of pro-inflammatory cytokines. This inflammatory response contributes to further tissue injury. There is also a systemic immune response to stroke, and there is a degree of immunosuppression that may contribute to the stroke patient's risk of infection. This immunosuppressive response may also be protective, with regulatory lymphocytes producing cytokines and growth factors that are neuroprotective. The specific targets of the immune response after stroke are not known, and the details of the immune and inflammatory responses are only partly understood. The role of inflammation and immune responses after stroke is twofold. The immune system may contribute to damage after stroke, but may also contribute to repair processes. The possibility that some of the immune response after stroke may be neuroprotective is exciting and suggests that deliberate enhancement of these responses may be a therapeutic option.