Selective interactions of electrolectins from eel electric organ and mouse thymus with mouse immature thymocytes

The pure electrolectin, a beta-D-galactoside binding lectin from the electric organ of the electric eel Electrophorus electricus, was found to agglutinate selectively a subpopulation of mouse thymocytes. This cell population could be separated from non-agglutinated cells by 1 g sedimentation over fetal calf serum. The agglutinated cells could be identified as immature thymocytes on the basis of the density of theta-antigen they bear on their surfaces, their mitotic activity and the absence of response to the mitogenic action of phytohemagglutinin. The immature mouse thymocytes were found to bind the endogenous mouse thymic lectin (MTL) a protein that displays the same saccharide specificity as the eel electrolectin and with which it cross-reacts immunologically. MTL is secreted by mouse thymic reticulocytes in tissue culture and its specific activity is markedly increased after depleting the thymus of its thymocytes. This finding is an indication of the possible localization of MTL in the thymic epithelium. These results are discussed in the light of our recent findings that the eel electrolectin has prophylactic and therapeutic actions on the experimental auto-immune myasthenia gravis in rabbits.