Immunohistochemistry of laminin in cortex lymph node (rat)

Anti-laminin-antibody and immunoperoxidase staining with diaminobenzidin (DAB) and hematoxylin counterstained on frozen section. Using an antibody against laminin brown-stained basement membranes (BM) are outlined demonstrating postcapillary venules (1) in the paracortical areas, as well as larger blood vessels. In between the blue-stained nuclei of different types of cells faintly brown-stained threads indicate patches of basement membrane-material produced by reticular cells. The inset shows the survey of tangential sectioned cortical area of the lymph node. Note that the BM of surrounding fat cells (3) is also slightly stained positive. Arrows (-->) indicate lymphocytes in diapedesis. Background: These specialized venules or so-called high endothelial venules (HEV) are lined by cuboidal or columnar endothelial cells that possess specific receptors for antigen-primed B- and T lymphocytes. These are the sites of entry of these lymphocytes into the lymph node (lymphocyte homing mechanism) where they leave the blood stream through these HEV and subsequently by diapedesis between the endothelial cells. B lymphocytes migrate to the lymphatic follicles in the cortex but T lymphocytes remain in the thymus-dependent area of the paracortex.