Surface markers of axolotl lymphocytes as defined by monoclonal antibodies.

In an attempt to identify urodele amphibian lymphocyte subpopulations by their surface markers, we prepared hybridomas from BALB/c mice spleen immunized with axolotl (Ambystoma mexicanum) blood and splenic leucocytes and purified immunoglobulins. Sixty-five hybridomas were selected and subsequently subcloned. Among numerous monoclonal antibodies (mAbs) thus obtained, four mAbs were extensively characterized by immunoblotting, single and double fluorescence and immunohistology. MAb 34.38.6 recognizes polypeptides between 65,000 and 72,000 MW and labels in immunofluorescence nearly all thymocytes, 60-63% splenic lymphocytes of normal animals but only 9% splenic lymphocytes in thymectomized animals. MAb 19.14.2 reacts with a 98,000 MW protein and labels a restricted lymphocyte population in thymus (52-77%) and spleen (20-25%). The immunohistological study demonstrates that 34.38.6 and 19.14.2 label most thymocytes and a large proportion of spleen leucocytes including lymphocytes, granulocytes and macrophages. In addition, 19.14.2 labels some large interdigitating cells in thymic epithelial areas and splenic cords. MAbs 33.45.1 and 33.101.2, respectively, recognize heavy (72,000-88,000 MW) and light (20,000-27,000 MW) axolotl immunoglobulin chains. They do not react with thymocytes but label a splenic lymphocyte population not labelled by mAb 34.38.6. The proportion of surface immunoglobulin-positive (sIg+) lymphocytes in spleen is not altered by thymectomy. MAb 33.101.2 labels 40-48% of splenic lymphocytes, 33.45.1 stains only 14% of these same cells. This suggests some interesting heavy-chain isotypic differences in axolotl. For the first time in urodele amphibians, mAbs differentiate T-like and B-like lymphocyte populations by their membrane markers. This will allow further analysis of the axolotl immune system.