ИСТИНА

Suicide has been proposed to result from an interaction of predisposing factors, or diathesis, and stress. Similar to psychiatric disorders, dysfunction of the immune system has been implicated in etiology and pathology of suicide. A hallmark of inflammation in the brain is “activation” of its main immune cells – microglia. We previously investigated complete coronal sections of prefrontal white matter in autopsy brains from suicides and a group of nonsuicide deaths matched on psychiatric diagnoses. We found that suicides had higher density of microglia-like cells associated with blood vessels in the dorsal prefrontal white matter. This finding prompted us to investigate the contribution of peripheral immune cells to the observed increase in microglia-like immunoreactive cells (Figure 1). The classical definition of inflammation presumes changes in the permeability of the blood-brain barrier followed by an influx of peripheral immune cells. Inflammation associated with neurological and infectious diseases is associated with a structural and functional loss in BBB integrity. Recently, animal models of stress-induced depression-like symptoms established a causal relationship between susceptibility to negative effects of stress and increased trafficking of monocytes into the brain. In humans, elucidation of the nature of infiltrating cells is hindered by the lack of a definitive marker of peripheral monocytes , since under normal physiological conditions, microglial cells express to a varying degree all of markers of peripheral monocytes with one notable exception - CD163. CD163 is a macrophage scavenger receptor that identifies brain perivascular macrophages and is not expressed in resting or activated parenchymal microglia. The aim of this study was to determine the contribution of peripheral monocytes to the increased perivascular cell density observed in dorsal prefrontal white matter of suicides. Increased densities of these cells could indicate an upregulation in brain-immune system cross-talk and, possibly, a breach in the BBB integrity in suicide.