Immunofluorescence characterization of innervation and nerve-immune cell interactions in mouse lymph nodes.

The peripheral nervous system communicates specifically with the immune system via local interactions. These interactions include the "hardwiring" of sympathetic/parasympathetic (efferent) and sensory nerves (afferent) to primary (e.g., thymus and bone marrow) and secondary (e.g., lymph node, spleen, and gut-associated lymphoid tissue) lymphoid tissue/organs. To gain a better understanding of this bidirectional interaction/crosstalk between the two systems, we have investigated the distribution of nerve fibres and PNS-immune cell associations in situ in the mouse lymph node by using immunofluorescent staining and confocal microscopy/ three-dimensional reconstruction. Our results demonstrate i) the presence of extensive nerve fibres in all compartments (including B cell follicles) in the mouse lymph node; ii) close contacts/associations of nerve fibres with blood vessels (including high endothelial venules) and lymphatic vessels/sinuses; iii) close contacts/associations of nerve fibres with various subsets of dendritic cells (e.g., B220+CD11c+, CD4+CD11c+, CD8a+CD11c+, and Mac1+CD11c+), Mac1+ macrophages, and B/T lymphocytes. Our novel findings concerning the innervation and nerve-immune cell interactions inside the mouse lymph node should greatly facilitate our understanding of the effects that the peripheral nervous system has on cellular- and humoral-mediated immune responses or vice versa in health and disease.