EXPRESSION OF TENASCIN IN DEVELOPING AND ADULT-MOUSE LYMPHOID ORGANS

The extracellular matrix (ECM) is essential in regulating many cell fu nctions in non-lymphoid cells, and the ECM may also play a role in the function of the immune system. Tenascin is a hexameric glycoprotein o f the ECM. In mouse, two major polypeptides of MW 210 KD and 260 KD ar e formed by differential splicing. Northern blot screening of various mouse tissues showed that the short 6 KB tenascin message was strongly expressed in the adult thymus, whereas very little or no tenascin mRN A could be detected in spleen. In addition, immunoblotting and histolo gical analysis with monoclonal anti-tenascin antibodies revealed the p resence of tenascin in lymph nodes and spleen. In thymus, only a short -splice variant of tenascin was detected by immunoblotting, which supp orted the Northern blot results. Immunohistology showed that the epith elial reticular stroma in both embryonic and adult mouse thymus expres sed tenascin, as did the postnatal mesenchymal reticular stroma in lym ph nodes and spleen. The distribution of tenascin in the thymus was mo re restricted than that of fibronectin and laminin.