12 



Con A has been extensively studied and characterized with 

 respect to ligand binding specificity (Goldstein et at., 

 1965; So and Goldstein, 1968), chemical structure and 

 properties (Edelman et al., 1972; Sharon and Lis, 1972) 

 and interactions with cell surfaces (Nicolson, 1974). The 

 effects of Con A on cells are widely varied and include 

 agglutination, induction of mitosis, alterations in cell 

 permeability and transport phenomena as well as cytotoxi- 

 city. The mechanisms of these complex interactions of 

 Con A are by no means clear but they all contain as a cen- 

 tral feature the binding of Con A to cell surface glycopro- 

 teins. Since the extent of the effect of Con A on a given 

 cell is related to the surface architecture, density and 

 mobility of the cell surface glycoprotein and glycolipid 

 constituents, it seems plausible that variations on Con A 

 receptors could lead to differential toxicity of Con A- 

 inhibitor conjugates. 



The observations that Con A induces agglutination of 

 some virally transformed cells at a concentration of lectin 

 much lower than that required for agglutination of normal 

 cells (Inbar and Sachs, 1969; Burger, 1969), implied that an 

 inherent difference in membrane architecture between normal 

 and transformed cells may exist. Attempts to quantitatively 

 detect a difference in the number of Con A binding sites on 

 normal cells and their virally transformed counterparts met 

 with limited success (Cline and Livingston, 1971; Ozanne and 

 Sambrook, 1971). Differences, if any, were extremely small 



