Isolation of large mononuclear Ia-positive veiled cells from the mouse thoracic duct.

Veiled cells (VC), are not normally present in the mouse thoracic duct lymph (TDL). However, TDL from mesenteric lymph-adenectomized (MLNX) mice contained about 1% VC. After exposure to whole body irradiation of 350-500 rads., or 800 rads., 1.5% and 7% VC respectively were present in the TDL. These cells could be enriched further by density gradient centrifugation on 14.5% metrizamide, about 60-70% VC being present in the cells from the interface. The VC had long sweeping cytoplasmic extensions or veils which were continuously extended and retracted when the VC were incubated at 37 degrees C. Electron microscopy revealed that the VC had a lobulated nucleus, and that the cytoplasm contained many mitochondria, a well-developed Golgi zone, rough endoplasmic reticulum and a few lysosomes. The cells were strongly Ia positive and over 70% showed adenosine triphosphatase activity. These features of the mouse VC from the TDL are similar to those described for VC isolated from different sources in other experimental animals and from the afferent lymph in man.