Antigen trapping cells in xenopus laevis: Tissue distribution

In the spleen of Xenopus laevis, antigen trapping (XL) cells are located at the periphery of the B-lymphocyte follicles and extend pseudopods through the boundary cell layer into the T-lymphocyte rich marginal zone to provide an anatomical bridge between the B-and T-cell compartments. The relationship between XL cells and nonsplenic antigen trapping cells was probed with a T-"independent" antigen, Aeromonas salmonicida. ¹²⁵I-Aeromonas were trapped in high concentrations in marrow, spleen and liver. Splenic trapping was most efficient at low doses and liver trapping at high doses of antigen. Immunofluorescence stains demonstrated large cells with trapped Aeromonas in spleen, marrow, liver, thymus, gut, kidney and blood. An antisera to XL cells stained large cells in all of these organs as well as vascular endothelium of the spleen, thymus, gut and lung. Thus, Xenopus has a widely distributed system of antigen trapping cells that may be related to some vascular endothelial cells.