γδ T Cell in Cerebral Ischemic Stroke: Characteristic, Immunity-Inflammatory Role, and Therapy

Immunity and inflammation are key elements of the pathobiology of stroke, a devastating illness second only to cardiac ischemia as a cause of death worldwide. While the immune system participates in the brain damage produced by ischemia, the damaged brain, in turn, exerts a powerful immunosuppressive effect that promotes fatal intercurrent infections and threatens the survival of stroke patients. Inflammatory signaling is instrumental in all stages of the ischemic cascade, from the early damaging events triggered by arterial occlusion, to the late regenerative processes underlying post-ischemic tissue repair. Recent developments have revealed that stroke, like multiple sclerosis, engages both innate and adaptive immunity. But, unlike multiple sclerosis, adaptive immunity triggered by newly exposed brain antigens does not have an impact on the acute phase of the damage. Nevertheless, modulation of adaptive immunity exerts a remarkable protective effect on the ischemic brain and offers the prospect of new stroke therapies. However, immunomodulation is not devoid of deleterious side effects, and gaining a better understanding of the reciprocal interaction between the immune system and the ischemic brain is essential to harness the full therapeutic potential of the immunology of stroke.

Background Lifetime stroke risk has been calculated in a limited number of selected populations. We determined lifetime risk of stroke globally and at the regional and country level. Methods Using Global Burden of Disease Study estimates of stroke incidence and the competing risks of non-stroke mortality, we estimated the cumulative lifetime risk of ischemic stroke, hemorrhagic stroke, and total stroke (with 95% uncertainty intervals [UI]) for 195 countries among adults over 25 years) for the years 1990 and 2016 and according to the GBD Study Socio-Demographic Index (SDI). Results The global estimated lifetime risk of stroke from age 25 onward was 24.9% (95% UI: 23.5–26.2): 24.7% (23.3–26.0) in men and 25.1% (23.7–26.5) in women. The lifetime risk of ischemic stroke was 18.3% and of hemorrhagic stroke was 8.2%. The risk of stroke was 23.5% in high SDI countries, 31.1% in high-middle SDI countries, and 13.2% in low SDI countries with UIs not overlapping for these categories. The greatest estimated risk of stroke was in East Asia (38.8%) and Central and Eastern Europe (31.7 and 31.6 %%), and lowest in Eastern Sub-Saharan Africa (11.8%). From 1990 to 2016, there was a relative increase of 8.9% in global lifetime risk. Conclusions The global lifetime risk of stroke is approximately 25% starting at age 25 in both men and women. There is geographical variation in the lifetime risk of stroke, with particularly high risk in East Asia, Central and Eastern Europe.