IMMUNOHISTOCHEMICAL LOCALIZATION AND BIOLOGICAL SIGNIFICANCE OF THE PHYLOGENICALLY CONSERVED THYMUS-BRAIN ANTIGEN (UB-13 ANTIGEN) IN SKATE,RAT AND HUMAN

A monoclonal antibody (UB-13) originally raised against the brain of t he skate (Raja kenojei, a cartilaginous fish) was found to react with lymphoid and brain tissues from many species when examined immunohisto chemically. In rat and human thymus, UB-13 antigen was observed to be closely associated with reticular tissue in the medulla and cortex, In terestingly, a few or several thymocytes were encircled by the UB-13-r eactive reticular tissue, At 14 days gestation, rat thymus consisted m ainly of reticular epithelial tissue, after which strong thymocyte pro duction started. At this stage, some of the reticular tissue was heavi ly stained with UB-13, In the thymus tissues of the irradiated and rec overing rats, where reduction and massive reproduction of thymocytes w ere observed, extensive UB-13 antigen expression localized on the reti cular epithelial tissue, an observation which may support the thymocyt e re-population. These findings suggest that the antigen recognized by UB-13 may be important for thymocyte proliferation and maturation. UB -13 antigen was found in the fibrous structure of the molecular and gr anular layer of the human cerebellum. Some glial cells were also stain ed strongly with UB-13 in the human cerebellar or cerebral grey and wh ite matter. In rat, glial cells, especially astroglias, and the endoth elial structure of blood vessels were stained strongly with UB-13. The se findings suggest that UB-13 may be a useful monoclonal antibody for analysis of brain-lymphoid antigen in many species.