60 D. A. L. DAVIES 



Tests with some monospecific H-2 antisera are shown in Table 

 V; quahtative inhibition entries are given in this table but again 

 the results clearly indicate that the H-2 inhibitors carry the 

 specificities expected from the known distribution of H-2 

 alleles. 



Table V 



HAEMAGGLUTINATION inhibition by H-2 ANTIGENS IN MONOSPECIFIC H-2 ANTISERA 



Serum specificity 



In the course of extraction and purification, where C3H mice 

 were mainly used with an H-2-K serum to follow activity, 

 products of LAN grown in C3H or outbred mice were used to 

 show lack of activity in the products of this "non-specific" 

 tumour. An unexpected fmding with the TM2 fraction of this 

 tumour ascitic fluid has been that it is not in fact devoid of 

 H-2 specificity, but is able to inhibit both H-2-C and H-2-F 

 haemagglutination. 



TMi fractions, when used to immunize mice from different 

 strains, have not yet induced an antibody response. TM2 

 fractions are antigenic and, injected into appropriate mouse 

 strains, induce antibodies whose haemagglutinating activity can 

 be inhibited only by material having the H-2 specificities of the 

 injected material. 



Discussion 



Homogenates of whole cells are extremely complex mixtures 

 of substances, from which the isolation of homogeneous com- 

 ponents is a most difficult task. This is particularly true if the 



