Thy-1 antigen: selective association in lymphoid organs with the vascular basement membrane involved in lymphocyte recirculation.

The cell surface differentiation antigen, Thy-1, was demonstrated by immunofluorescence to be associated with collagen-based connective tissue (mainly basement membrane) around some blood vessels in rat lymphoid organs. This association is highly selective: only certain types of blood vessel within a given lymphoid organ were found to be Thy-1+; and different lymphoid organs (thymus, bone marrow, lymph node and spleen) had characteristic differences in the types of blood vessel that bear Thy-1. In lymph node and spleen the vessels that were Thy-1+ were those involved in lymphocyte recirculation and homing (post-capillary venules and arterioles of white pulp); the possibility that Thy-1 may function in mediating selective adhesion of small lymphocytes to extracellular substrates during recirculation is discussed.