H-2 ANTIGENS OF THE MOUSE 63 



the lipid contributes in some way to the configuration of the 

 protein, so that both parts are necessary. It would be admirably 

 consistent with the dramatic effects, e.g. of runt disease, for the 

 point of attack to be the membraneous structures of the cell which 

 carry the ribosomal synthetic inachinery. 



It will be of the greatest interest to test the products obtained 

 using transplantation, enhancement and haemagglutination 

 inhibition tests for each of these three activities, because certain 

 differences undoubtedly exist between the T, E and H antigens 

 so far prepared. E antigens can be frozen or freeze-dried with 

 impunity whereas T and H antigens can not. T antigen is stable 

 to ultrasonics whereas H-2 antigen is labile. E antigen can be 

 lipid-extracted but this destroys activity of H-2 preparations. 

 These facts do not necessarily weigh against the view that the 

 same specificity is involved as one can imagine that differences in 

 state of aggregation or degradation might markedly affect the 

 nature of the immune response of an animal. A recent observa- 

 tion (Haskova and Hilgert, 1961) that a hastened rejection of skin 

 grafts in mice can be obtained by immunization with ascitic 

 fluid is consistent with results (to be published) indicating that the 

 material described here does indeed carry T activity. 



The H-2 specificities found to be carried by the products 

 described agree with the known distribution of H-2 alleles in the 

 mice used. It is not clear, however, if the products represent 

 families of closely similar molecules each carrying one specificity 

 or whether the several specificities belonging to one mouse strain 

 reflect different structural features of one molecular entity. Studies 

 in other branches of immunochemistry would suggest the latter 

 as much more likely but a genetic basis of pseudo-alleles, where 

 crossovers sometimes occur, does not permit one to discount the 

 first possibility. 



An unexpected finding has been the presence of H-2-C and 

 H-2-F specificity in the product of the "non-specific" LAN 

 tumour, which has been used as a source of presumed serologically 



