Post-capillary venules of the mouse lymphatic tissues with special reference to the distribution of their endothelial IgG.

Post-capillary venules (PCV) of the lymph nodes and Peyer's patches were studied in frozen sections stained with an indirect immunoperoxidase technique to demonstrate their endothelium-associated IgG in DBA/2 mice rendered T-lymphocyte depleted with anti-theta- and anti-thymus-globulins. Three types of IgG-distribution (luminal, intraendothelial and basement membrane, types I, II and III, respectively), each confined to one of the three PCV grades (graded on the basis of the endothelial cell height), could be distinguished. The PCV grades, on the other hand, were closely correlated with the degree of T-lymphocyte depletion. The significance of this intimate relationship between the IgG-distribution pattern and the PVC grades was discussed in regard to the T-lymphocyte recirculation. A hypothesis was presented describing the presumed sequence of events involved in the passage of T-lymphocytes through the endothelium of the PCV which is the crucial step in their recirculation from blood of the lymphatic tissue.