900 THE HUMAN BLOOD GROUPS 



more sensitive type of cells. However this may be, the hypothetic additional agglutino- 

 gen (termed as C or X or A') should not be put on the same level with the agglutino- 

 gens A and B as Guthrie and Huck propose, since there is no definite proof yet that A' 

 occurs independent of A. If A' were an independent mendelizing factor it ought to be 

 found with regularity in groups other than A and AB. The two agglutinins acting on 

 group A cells which may be designated by a and a^ are present in nearly all sera of 

 groups O and B. Guthrie and Huck and Simson' described sera containing only a^ or 

 a. In the former case the serum agglutinates selectively the cells AA'. 



With regard to other findings of blood differences by means of absorption,^ it 

 should be borne in mind that they may be the result of quantitative variations, as has 

 been pointed out by Mino and Lattes and Cavazzuti, and that thorough investigation 

 is needed in- every case to exclude this possibility. 



"cold" agglutinins 



It has been mentioned above that at low temperature (o°-5° C.) a serum aggluti- 

 nates, as a rule, the individual's own corpuscles as well as others of the same species. 

 When a number of corpuscles are tested, differences are noticed in the degree of the 

 reaction, which indicate a certain specificity ;3 the differences may be more marked 

 with the use of properly absorbed sera. In this way, besides other slight variations, 

 two sorts of group-A corpuscles can be demonstrated corresponding to those discussed 

 in the previous paragraph. ■< Frequently the sera belonging to the cells AA' act more 

 intensely on the other type, which may be termed AA^ than on AA', and vice versa; 

 moreover, the former sera react markedly on cells of group (Table IV). 



Using the same method for sera and corpuscles B (and O) a number of individ- 

 ual variations were observed without apparent regularity. A proper classification of 

 all these reactions which indicate the existence of a number of individual blood dif- 

 ferences is not possible as yet and would serve no practical purpose. 



The fact that agglutination of red cells tends to disappear on warming and that 

 agglutinins are liberated from their combination with the cells has been established 

 also for normal heteroagglutinins.s This reversion of the agglutinin reaction is well 

 marked at temperatures around 50° C.; cold agglutination, on the other hand, is 

 much more sensitive to the influence of temperature so that it is rarely encountered 

 under conditions of routine technique, i.e., at room temperature, and practically does 

 not interfere with the group scheme.^ But some particularly strong reactions may 

 persist when the tests are made at not-too-high room temperatures. In our opinion, 

 a number of observations on slight atypical isoagglutination — "minor" agglutination 



• Simson, F. W.: /. Path. &° Bad., 29, 279. 1926. 



^ Guthrie, C. G., Pessel, J. F., and Huck, J. G.: Bull. Johns Hopkins Uosp., 35, 221. 1Q24; Bunker, 

 H. A., and Meyers, S.: J. Lab. b° Clin. Med., 12, 415. 1927. 



i Bialousknia, W., and Hirszfeld, L. : Przcgladu Epidcmjologiczncgo, i, 437. 1921 ; Guthrie, C. G., 

 Pessell, J. F., and Huck, J. G.: Bull. Johns Hopkins Hosp., 34, 37, 80, 12S. 1923; 35, 2^^, s^, 81, 126, 

 221. 1924; Landsteiner, K., and Levine, P.: J. Immunol. 12,441. 1926. 



•t Landsteiner, K., and Levine, P.: loc. cit. 



s Landsteiner, K.: Miinchen. nied. Wchnschr., No. 46. 1902; Jervell, F.: J. Innniinol., 6, 445 

 1921; cL Doelter, W.: Zlschr.f. Immunitdtsjorsch. 11. c.Kper. Therap., 43, 128. 1925. 



''The exceptional cases of unusually stronj; autoagglutination have been referred to above. 



