The distribution of brain-associated theta antigen cross-reactive with mouse in the brain of other species

θ is a mouse alloantigen which serves as a marker for thymus-derived (T) cells (1). Anti-θ antisera have proven to be powerful tools in elucidating the roles of bone marrow-derived (B) and T lymphocytes (2). θ is shared by T lymphocytes and brain tissue in the mouse (1). We had previously shown (3) that immunization of rabbits and goats with mouse brain results in the production of potent anti-θ-like antisera. We have termed these anti-brain-associated θ antisera (BAθ). It would be a great advantage in studying immune systems other than the mouse if antigen comparable to θ were available. We have taken a variety of approaches in an attempt to develop anti-θ-like antisera to other species. One of these is to investigate brain tissue of other species to determine if it contains cross-reacting antigens with mouse BAθ.