Q^UALITATIVE IMMUNE RESPONSES 



body. They form a motley group, most of which have been 

 recognized by the abiUty of certain apparently normal sera 

 to agglutinate foreign red cells or some bacterial strains. It 

 also includes the human woagglutinins and the interesting 

 T agglutinins of most mammalian sera which agglutinate 

 red cells altered by the enzyme RDE. In general, the 

 behaviour of natural antibody is indistinguishable from that 

 of a classical antibody of relatively low titre and low avidity. 



Properdin presents a special problem. This is a high 

 molecular weight globulin, making up only about o-02 % of 

 the serum proteins, which reacts with a wide range of bacteria 

 and viruses in a fashion very similar to that of specific anti- 

 body. In fact Talmage has recently asked very pertinently 

 whether there is any reason why properdin should not be 

 called an antibody. 



(2) The standard responses of hay-fever subjects to the 

 pollen extracts involved closely resemble Kuhns and 

 Pappenheimer's (1952) observations with diphtheria toxoid 

 in allergic subjects. The antibody in serum is associated with 

 a globulin fraction which has been variously identified as of 

 ^ or yi in type, with recent work suggesting that the latter 

 is correct. Loveless's work (1940) indicates that pollen 

 extracts administered parenterally to hay-fever patients 

 produce classical type antibody which has a blocking effect 

 in preventing, to a large extent, the access of the antigen 

 to the loci responsible for symptoms. This principle, that one 

 type of antibody may modify the activity of an immuno- 

 logical response to the same antigen, is one which may 

 have important bearing on some of the problems associated 

 with pathological disturbances of the immune mechanism. 



The principal characters of the hay-fever type response 

 are absence of standard aggregation type reactions and very 

 weak complement fixation ; increased tendency for antibody 

 to be taken up by tissue cells — for example, as exploited in 

 the Prausnitz-Kustner phenomenon; and in human beings 

 its failure to pass the placenta. Although most work on this 



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