THE BASIS OF SPECIFICITY 



255 



SO5H 



in the test-tube in virtue of anti- 

 body groupings that unite specific- 

 ally with unaltered horse globulin. 

 But if atoxyl is also coupled to 

 chicken globulin, and the atoxyl- 

 azo-protein so prepared is used in 

 the in vitro tests, the precipitation 

 that occurs will depend solely on 

 antibody groupings acting specific- 

 ally on atoxyl, since horse globulin 

 and chicken globulin show no anti- 

 genic relationship. 



Using these methods, it has been 

 possible to prepare antisera that give 

 specific precipitation with synthetic 

 antigens in which the active groupings 

 are provided by such substances as 

 metanihc acid, atoxyl, Isevo-, dextro- 

 and meso-tartaric acid, glucosides, 

 galactosides, and so on (Landsteiner 

 and Lampl 19176, Landsteiner 1919, 

 1930, Landsteiner and van der Scheer 

 1928, 1929, 1931, 1932a, b, 1934a, b, 

 Avery and Goebel 1929, Avery, Goebel 

 and Babers, 1932, Goebel, Avery and 

 Babers 1934), dipeptides and penta- 

 peptides (Landsteiner and van der 

 Scheer 1932a, 1939), pjTazolon com- 

 pounds (Erlenmeyer and Berger 1934, 



Harte 1938), pyridine (Landsteiner and Pirie 1937), strychnine (Hooker and Boyd 1940), 

 thyroxm (Glutton, Harington and Yuill 1938), asphin (Butler, Harington and YuiU 

 1940, and histamme (Fell et al. 1943). 



These results clearly demonstrate an immunological specificity dependent upon chemical 

 groups of known structure. In the last tlu-ee examples the specific action of the antibodies 

 concerned could be shown by a marked reduction of pharmacological activity of the 

 thyroxin, aspirin and histamine in ammals treated with antisera prepared against thyroxyl 

 protein, aspiryl protein and histamine protein respectively (see also Singer, p. 259). 



The comparison of antigens modified by optically active isomers, as, for instance, 

 with dextro-, meso- and Isevo-tartaric antigens, or with glucoside and galactoside 

 antigens (see also Woolf, Marrack and Downie 1936), in which the isomers differ 

 only in the arrangement round a single carbon atom, shows clearly that, as might 

 be expected, stereo-chemical differences in structure are important determinants 

 of immunological specificity. 



Specificity depends in part on the nature of any grouping in a complex organic 

 molecule, and in part on the position in the molecule which the grouping occupies. 

 Fig. 42 gives an example — the cross precipitations observed with an antigen prepared 

 from o-amiuo-benzene-sulphonic acid (see Landsteiner 1919, Marrack 1934). 



In the centre of the figure, labelled [G], is represented the active grouping of 

 the azo-protein used as an antigen in the precipitation tests. Around it, labelled 

 [A], are placed antibodies prepared against antigens synthesized by coupUng 

 the groupings shown to some unrelated protein. The double-headed arrows in- 



