Lymphoid tissues innervation

Psychological stress may influence the immune system by activation of the hypothalamic-pituitary-adrenal (HPA) axis and the sympathetic-adrenal-medullary axis (SAM). The well-described innervation of primary and secondary lymphoid tissues by the autonomic nervous system also has been implicated in stress-related modulation of the immune response. These pathways operate by producing biological mediators that interact with and affect cellular components of the immune system.13... 

Most lymphoid tissues are innervated by the sympathetic nervous system, both directly and indirectly. These same tissues express receptors for a variety of hormones, including classical... 

The activation of the stress systems affects all tissues of the organism, and the peripheral immune system is no exception. These effects are mediated through at least tw o pathways via the HPA axis and by virtue of the innervation of lymphatic tissues by autonomic nerve fibers, especially from the sympathetic nervous system. All lymphoid tissues, primary (bone marrow and thymus) as well as secondary (spleen, lymph nodes, and gut-associated lymphoid tissue) are innervated by sympathetic nerve fibers. As discussed above, most lymphoid cells express catecholamine receptors, including B-lymphocytes, CD4- and CD 8-positive T cells, dendritic cells, monocytes, and macrophages. 

Important interactions of the nervous and immune systems are known to take place and to involve neuropeptides the largest body of available evidence relates to the participation of substance P in these interactions. Most lymphoid tissues are innervated by substance P positive nerves substance P has also been immuno-localized to immune and inflammatory cells. Cells of the immune system express receptors for substance P, and relatively low concentrations of this peptide alter the functional capabilities of these cells. 

Nilsson, G., Alving, K., Ahlstedt, S. et al. (1990). Peptidergic innervation of rat lymphoid tissue and lung relation to mast cells and sensitivity to capsaicin and immunization. Cell Tissue Res. 262, 125-133. 

The innervation of the lymphoid vasculature by substance P-containing neurons and the ability of substance P to enhance lymph tissue blood flow (Lundbeig et al., 1985) suggest that substance P may alter lymphocyte traffic . Substance P induces the expression of endothelial leukocyte adhesion molecule 1 (ELAM-1) on microvascular endothelial cells (Matis et al., 1990) and may similarly affect the expression of adhesion molecules on lymphocytes. Infusion of substance P has been shown to increase lymph flow and lymphocyte traffic in sheep lymph nodes (Moore etal., 1989). 

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