Stroke systemic immune system

Under physiological conditions there is a small resident population of macrophages— microglia and perivascular macrophages—along with some roaming T cell lymphocytes in the central nervous system. However, most of the immune cells involved in inflammation after stroke are in fact derived from the systemic circulation. 

These changing concepts of the role of the immune system and inflammation in stroke and cerebrovascular disease have led to searches for new treatment and prevention strategies. This chapter will review the current state of knowledge about inflammation and the immune system in stroke and atherosclerosis and discuss potential therapeutic strategies. 

Stroke-related inflammation in the brain appears to largely result from a selective migration and infiltration of systemic (i.e., circulating) leukocytes to the focus of cerebral ischemia. These cells are predominantly those of the innate immune system, at least initially. Activated neutrophil polymorphs begin to infiltrate as early as 4h after stroke, initially being... 

Stroke induces an acute stress response—i.e., over-activation of the sympathetic nervous system and increased corticosteroid levels (with resultant neutrophiha and lymphocytopenia). This in turn leads to depressed immunity and altered immune responses during the acute phase of stroke and may predispose patients to infections, particularly pneumonia, which is the commonest cause of mortality after the first few days of stroke (Meisel et al., 2005). In the clinical setting, increased total white cell counts and neutrophilia, which correlate with infarct size, are independently associated with worse outcome after stroke. Recently a massive and early activation of the systemic immnne system has been shown to occur also in experimental stroke (Offner et al., 2006). 

The study of cerebrovascular disease has advanced markedly in recent years with advances in non-invasive imaging methods such as MR angiography and CT angiography as well as an improved understanding of the immune system in the pathogenesis of atherosclerosis. Atherosclerotic cerebrovascular disease is a common cause of strokes and shows a predilection for sites such as the bifurcation of the common carotid artery into the internal and external carotid arteries and the aortic arch and the major intracranial arteries such as the basilar artery and the middle cerebral arteries. Occlusive atherosclerotic vascular disease of these large extracranial arteries is responsible for as many as 20-30% of ischemic strokes and intracranial steno-occlusive disease causes around 5-10% of ischemic strokes. 

Many aspects of the role of inflammation and the immune system in stroke remain controversial (Chamorro and Hallen-beck, 2006). However, more refined characterization of immune responses after stroke may suggest new and different therapeutic targets for acute ischemic stroke, in addition to novel approaches that are ongoing for the prevention of cardiovascular disease. 

Discuss the role of the immune system before and after ischemic and hemorrhagic stroke. 

Offner H, Subramanian S, Parker SM, Afentoulis ME, Vandenbark AA, Hum PD (2006) Experimental stroke induces massive, rapid activation of the peripheral immune system. J Cereb Blood Flow Metab 26 654-665. 

In the previous section we looked at innate immunity. This aspect of the immune system was the poor cousin to acquired immunity for decades, but has recendy graduated to a much higher status because of its relationship to inflammation. Many of the processes involving macrophages and other innate immunity cell types lead to inflammation. Inflammation is known to be the underlying contributor to almost every chronic human disease known, including arthritis, Crohn s disease, diabetes, heart disease, Alzheimer s disease, and stroke. It has recently been shown that inflammation is also linked to cancer. 

One relatively new discovery is the power of pine bark in treating disease. Pine bark is higher than any other plant except grapeseed in proanthocyanidin, a powerful antioxidant and potentiator of vitamin C. Free radicals have been implicated in scores of diseases such as cancer, Alzheimer s disease, Parkinson s disease, arthritis, cataracts, heart disease, and stroke. The human immune system uses antioxidants to deactivate and eliminate free radicals from our bodies. This antioxidant... 

This is a supplement containing more than forty water-soluble antioxidants. It is a complex of antioxidant flavonoids obtained from the bark of French maritime pine trees. These flavonoids are credited with reducing stroke and heart disease and improving the immune system to effectively fight viruses. 

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