The Effect of Veiled Cells on Lymphocyte Function

The afferent lymph supply is essential for the proper functioning of the lymph node. Ablation of the afferent vessels leads to the disappearance of macrophages, interdigitating cells, plasma cells, germinal centres and high endothelial venules (1,2). The majority of T and B lymphocytes enter the node via the blood vessels, but this route is not used by the accessory cells, many of which are derived from precursors in the afferent lymph (3). The lymph contains large cells with actively moving cytoplasmic extensions, or veils. Cells of this type are not found in the efferent or thoracic duct lymph and appear to end their journey in the paracortex, or T-dependent area of the lymph node (4), where they may differentiate into interdigitating cells. Actively phagocytic cells form only 20% of veiled cells and 98% are strongly la-positive (3,5).