Heterogeneity of concanavalin A receptors on Ehrlich tumor cells

Concanavalin A (Con A)-binding glycoproteins have been purified from Ehrlich ascites tumor cells by precipitation of cell extracts with Con A in agarose gels and by lithium diiodosalicylate (LIS) extraction. Antisera prepared against these two glycoprotein fractions indicate the presence of a minimum of five different antigens in the Con A-cell extract precipitate and a minimum of three different antigens in the LIS-extracted preparation. That both kinds of antisera are directed towards surface membrane antigens is strongly suggested by the fact that they give precipitin bands with purified plasma membrane from Ehrlich cells, they agglutinate whole cells, and they no longer give precipitin bands after absorption by whole cells. Cell extract material which was specifically eluted from a Con A-Sepharose 4B column with alpha-methylmannoside was recognized by antisera to both glycoprotein preparation, demonstrating that the antigens were Con A-binding components; material which did not bind the column failed to react with either antisera. Immunochemical analysis indicated that one of the antigens present in the LIS-extracted material was distinct from the five antigens prepared by lectin precipitation in agarose gels suggesting that a minimum of six individual Con A receptors are present on the surface of Ehrlich tumor cells. Immunochromatography was found to be a convenient method to purify the antigens obtained by the LIS extraction of Ehrlich cells.