1906.] On Opsonins in Relation to Red Blood-cells. 9 



1 per cent, of its original value, but beyond this its titre cannot be further 

 defined from the experiments made ; and similarly with the remaining sera. 



The experiments in Table III show that a very rapid removal of opsonin 

 takes place during the first five minutes, and that subsequently the removal 

 of opsonin becomes considerably slower, some of the opsonin originally present 

 still remaining in Sera D and H even at the end of several hours.' As would be 

 expected, the removal rate is seen to be more rapid with the more concentrated 

 serum (A to D) than in the more dilute serum (E to H, and I to M). 



The experiments in Table III show that, when spontaneous phagocytosis 

 is avoided, the estimation of red blood -cell opsonin may be carried out. 

 Sera from different sources may be compared as to their opsonic content by 

 determining the minimum amount of serum required to sensibilise a given 

 bulk of red cells so as to produce the maximum degree of phagocytosis. 

 An alternative method is to determine the minimal bulk of red blood-cells 

 required to deopsinate unit of volume of the sera. 



The Interaction of Bed Blood-cell and Opsonin. 



It is not possible from the data above given to arrive at a definite 

 conclusion as to the nature of the process occurring when red blood-cells 

 are sensibilised by opsonin. 



It has been already pointed out that even considerable dilution of the 

 serum of Eabbit A did not abolish sensibilisation so long as the ratio 



B 



g-= 1 was preserved. This circumstance is readily explicable on the 



assumption that a chemical reaction takes place, but it is also equally well 

 explicable on the assumption that a physical process of adsorption or 

 selective solubility occurs. The relation between concentration and 

 adsorption has been determined by Ostwald* to be 



Ci = aC 2 n , 

 where Ci is the concentration of the adsorbed substance, C 2 that of the 

 substance in solution, and a and n are constants. By suitably choosing 

 the values of a and n, the value of Ci could be left practically unchanged 

 when C 2 was reduced to 1/500 of its initial value.f So far as the behaviour 

 of opsonins in respect of dilution has up to the present been investigated, 



* ' Lehrbuch d. allg. Chemie,' 1891, vol. 1, 2te Auflage, p. 1096. 



C 

 t For example, if a = 1,000,000 and n = 1, in which case (since ^ = iooqoqo) a li but 



2 



1 x 10 c of the opsonin originally present in the liquid would pass to the red blood-cells. 



If n were less than 1, the proportion taken up by the red cells would be still greater. 

 Unfortunately the estimation of very small percentages of opsonin requires much larger 

 amounts of serum than can be obtained from rabbits. 



