H-2 ANTIGENS OF THE MOUSE 59 



is a Structural component of mouse cells, believed to be associated 

 with cell membranes, but it can be found in soluble form where 

 rapid growth is in progress, e.g. serum of pregnant mice, and 

 ascitic fluid. It is a protein and has species specificity but no 

 special specificity for different mouse strains. The activity of the 

 TM2 fraction with respect to this specificity indicates that it must 

 be the protein component of the H-2 lipoprotein. 



Table IV 

 Inhibition of haemagglutination by H-2 antigens in polyspecific H-2 



ANTISERA 



4,000 2,000 1,000 500 250 125 62 31 16 8 4 

 Antigen from C3H (H-2-CD^EfK), concentration in [jLg./nil. 

 *Serum i — — — — — — — — — i 3 



tSerum 2 — — — — — — 12344 



iSerum3 i 3 333434444 



Antigen from C57 (H-2-cDbEFk) 



Serum i — — 3 44344444 



Serum 2 — — — — — — — — i 3 4 



Serum 3 — — 2 23443444 



Antigen from BALB/c (H-2-CDEdFk) 



Serum i 3 34 34443444 



Serum 2 3 43 34434434 



Serum 3 — — — — — — — 1244 



* BALB/c anti-CsH serum at i : 150, tested with C3H red cells, (detect D^EK) 

 t BALB/c anti-C57 serum at i : 50, tested with C57 red cells, (detect DbE) 

 i C3H anti-BALB/c serum at i : 150, tested with BALB red cells, (detect DEdp) 

 Degrees of agglutination from 4 = maximum to i = minimum. 



The specificity of the products of the different mouse strains has 

 been tested using some of the sera shown in Table I. The homo- 

 logous and heterologous reactions with three polyspecific H-2 

 antisera are shown in Table IV, from which it is clear that strong 

 inhibition of haemagglutination occurs when the inhibitor is 

 prepared from the mouse strain used for immunization and weak 

 inhibition where cross-reactions might be anticipated. These 

 highly active inhibitors are quite inactive in systems where no 

 cross-reactions are to be expected. 



