Effect of heat on flocculating antibodies of rabbit antisera

Earlier workers have found that antisera to different antigens vary in their resistance to heat. In general it has been found that bacterial somatic agglutinins lose their flocculating power with less heating than flagellar agglutinins. For example, Jones (1927) showed that flagellar agglutinin to hogcholera bacillus still agglutinated after the antiserum was heated at 900 C. for 20 minutes, whereas somatic agglutinin did not after the same time at 750 C. It has been also shown that some antisera which have lost their ability to agglutinate after heating for several minutes at 70-80° C. still combine with bacteria to give the phenomenon of inhibition (Eisenberg and Volk, 1902; Jones, 1928). This ability to inhibit is destroyed at 900 C., i.e. approximately the temperature needed for destruction of flagellar agglutinins. Bawden and Pirie (1938b) showed that plant viruses with rod-shaped particles form with their antisera fluffy, open floccules similar to those formed by the agglutination of bacterial flagellar antigens. whereas those with spherical (or almost spherical) particles form dense granular precipitates similar to those formed by the agglutination of bacterial somatic antigens. When antisera to these two types of viruses are heated, they behave in the same way as antisera to the two types of bacterial antigens. Strong antisera to rod-shaped tobacco mosaic virus flocculate until heated for 10 minutes at 90° C., whereas antisera to the spherical tomato bushy stunt virus do not flocculate after heating for 10 minutes at 750 C. This paper describes experiments made to investigate the causes underlying the differences in the apparent behaviour of different antisera on heating.