109 



H-7 that is resistant to Con A induced cytotoxicity, is 

 presented in Figure 23. During the 15 minute exposure the 

 H-7 cells bound a maximum of 16 x 10 molecules Con A per 

 cell whereas the H-7Wcr bound a maximum of 14.8 x 10 

 molecules per cell. Furthermore, the binding by II-7Wcr 



reached a plateau at 37)jg/ml Con A while the H-7 cell 



125 

 binding did not appear to level off. The I-Con A bind- 

 ing for both cells was inhibited 89% by preincubation with 

 Con A (100ug/rtil, 30 minutes) and was inhibited only 21% by 

 prior exposure to BSA (lOOpg/ml, 30 minutes). Both cell 

 lines appear, within limits of error, to bind essentially 

 the same amount of Con A over the range of concentrations 



investigated. 



125 

 Figure 24 depicts the binding of I-Con A by rat 



fibroblast cells, A-9, and their amanitin resistant subline, 



125 

 LAN 2. Both cell lines were exposed to I-Con A for 15 



minutes at 22°C. The results indicate that both cell lines 



125 

 bound an equivalent number of I-Con A molecules with a 



maximum of 12.6 x 10 molecules per cell being obtained. 

 This amount is somewhat less than that bound by the CHO 

 cells. In addition, the rat cells bound fewer Con A mole- 

 cules over the entire range of concentrations tested than 

 did the CHO cells. The binding was inhibited completely 

 by pretreatment with Con A (lOOpg/ml, 30 minutes) and only 



inhibited 12% by prior exposure to BSA. 



3 

 The binding of H-DM-ADGG-Con A was examined only with 



H-7 CHO cells due to the limited quantities of labeled 



