322 ISOELECTRIC POINT OF RED BLOOD CELLS 



values shows the same inflection at pH 4.7 as Fig. 4, and is therefore 

 omitted. 



This effect is very difficult to analyze. It appears to be a chemical 

 one, and may involve the formation of a small amount of protein 

 chloride on the alkaline side of the isoelectric point, due to the excess 

 of chlorine ion, but since the effect is noted on both sides of the iso- 

 electric point, any explanation of it in the light of the facts presented 

 here would be largely speculative. 



The agglutinability of sensitized cells in the presence of an electrolyte 

 as compared with the stability of normal cells is not an absolute dif- 

 ference, even when the electrolyte is NaCl. Specific agglutination is 

 known to occur over a wide range of pH values, as shown by Krum- 

 wiede and Pratt^^ among others; that it is not independent of the 

 hydrogen ion concentration, however, is indicated as shown above by 

 the existence of an optimum, at which it is practically independent of 

 the presence of neutral salt. On either side of this range as common 

 experience shows it is accelerated by the presence of neutral salt. 

 Similarly normal cells which may not agglutinate in salt-free media at 

 pH 4.9 have been found in our titrations to agglutinate readily at pH 

 5.5 in the presence of NaCl. At less acidities, while flocculation may 

 not occur, we have found the speed of settling to be affected in a simi- 

 lar way by the hydrogen ion concentration. 



It is apparent then when we compare the influence of the hydrogen 

 ion concentration upon the electrical charge and chemical behavior 

 of red cells with the influence upon agglutination that we have to 

 deal not with one phenomenon, but with two, which are, however, 

 closely related. 



CONCLUSIONS. 



1. The movement of normal and sensitized red blood cells in the 

 electric field is a function of the hydrogen ion concentration. The 

 isoelectric point, at which no movement occurs, corresponds with pH 

 4.6. 



2. On the alkaline side of the isoelectric point the charge carried is 

 negative and increases with the alkalinity. On the acid side the 

 charge is positive and increases with the acidity. 



^^ Krumwiede, C, Jr., and Pratt, J., Z. Immunitdtsforsch., Orig., 1912, xvi, 517. 



