Summary
Guinea pigs and rabbits were used as experimental animals for a reinvestigation of the serologic diagnosis of murine typhus and RMSF, principally by means of the complement fixation test.
In CF block titrations it was observed that method 1 antigens gave results significantly different with early sera than with late sera. With early convalescent or acute sera the antigen titer varied with the concentration of serum; it was uniformly the highest with the lowest dilution of serum tested (1:2) and decreased in a step-wise fashion when the serum was further diluted. With late convalescent sera the antigen titer did not vary in this manner but rather tended to be the same in both the lowest as well as in the highest serum dilution in which CF was observed.
With early sera even the lowest dilution of sera did not give as great an antigen titer as the late convalescent sera.
These differences in the results of block titrations of early and late specimens make it difficult to define a unit of antigen that will apply both to early and late serum specimens.
Antibody was detected earlier in the course of the experimental disease in guinea pigs when increased amounts of method 1 antigen were employed. This was observed consistently in both murine typhus and RMSF.
