Serologic Patterns of Human Sera

Certain of the serological factors which vary with the individual have been reported,t together with data supporting the idea that age, sex, and blood group differences show some correlation with the antibody titers measured. This supplementary note deals with one of the antigen-antibody systems included in the former study, the essential feature here being the significance of the host origin of the antigen and of the antibody used. Specfically, herein are recorded titrations of the heteroagglutinin of human sera for sheep cells and of the corresponding heteroagglutinin of sheep serum for human cells. Such cross-reactions serve to measure reciprocal relations, and thus offer suggestions as to the quantity and the quality of the antigen and of the antibody as found in two species which are, in general, serologically unrelated. The results here tabulated embrace cross-titrations of 160 human sera and erythrocytes with the serum and red cells of a single sheep. The methods of testing and of evaluating the results in terms of "units" have been described. It may be stated at once that there is no fixed relationship between the amount of antibody present in a given human serum capable of agglutinating sheep cells and the amount of antigen in the cells of the same blood sensitive to agglutination by sheep serum. This statement is, evidently, equally true for the capacities of the sheep serum and the sheep cells in their reactions with human antigen and antibody. Each varies, and varies independendy; thus, in a given human blood the relationship between antibody and antigen may be 0:256 (expressed in "units"), with another blood it may be quite the reverse, 256:0; or, and this is far more often the case, the ratio may be essentially a 1:1 balance with the unit titers of the order 34:40, or 120:136. And yet, despite such a degree of variability, it appears that the relative values found when a reasonably large number of sera (or of cells) of a given dass is tested and compared with other classes, differences appear which can hardly be regarded as random.