MECHANISM OF ANTIGEN-ANTIBODY REACTIONS 219 



the antigen's being in the colloidal state. In the lihenomenon of 

 adsorption of antibodies by the cell which occurs in Bordet's phase 

 one, the student should remember that the immune serum will con- 

 tain antibodies for eacli Iriio antigenic constituent of the cell. 



Summary 



Some of the important points about the mechanism of cellular 

 agglutination by immune serum may be summarized as follows: 



1. There are two phases to the reaction as suggested by Bordet. 



2. The antibodies are ]:)resent in the immune serum intimately 

 associated with the globulin fraction. 



3. During the first phase the cells specifically adsorb the anti- 

 ])odies corresponding to the antigens present as a surface film com- 

 ]iosed of antibody globulin. This readily occurs at 0° 0. and also 

 at 37° C. to 56° C, and also thi'ough a fairly wide range of pH 

 values. It is probably of molecular lliickness since i1 is not de- 

 tectable by microscopic examination. 



4. When the anti])ody glo])ulin is adsorbed, it seems to ])ccome 

 denatured and causes tlie cells that have adsorbed it to behave as 

 particles of denatured serum globulin with an increase of the co- 

 hesive forces under proper conditions. 



5. The presence of a proper concentration of sodium chloride 

 leads to a change in membrane potential to within a critical value 

 of 13 to 15 millivolts Avithout a reduction of the cohesive forces. 



6. This alteration of membrane potential to within the critical 

 value in combination with the increased cohesive force is respon- 

 sible for the clumping and sticking together of the cells. 



7. Reference is made to the newer concepts of cell sensitization 

 and agglutination offered by Heidelberger and Kendall. 



References 



Bechold, H.: Die Ausflockung von Suspensionen bzw. Kolloiden und die 

 Bakterienagglutination, Ztschr. f. Physick. Chem. 48: 385, 1904. 



Bordet, J.: 1895. Cited by Bordet, Studies iu Immunity, New York, 1909, 

 John Wiley & Sons, Inc. 



Bordet, J.: Le Mecanisme de 1 'agglutination, Ann. Inst. Pasteur 10: 193, 

 1896. Ibid. 13: 225, 1899. Also Studies in Immunity, translated by 

 Gay, New York, 1909, John Wiley & Sons, Inc., pp." 142-164. 



Buchanan, E. E.: Agglutination, J, Bact. 4: 73, 1919. 



Coulter, C. B.: The Isoelectric Point of Eed Blood Cells and Its Relation to 

 Agglutination, J. C4en. Physiol. 3: 309, 1921, 



