Protection of Mice Against H. Pertussis by Serum. Comparison of Protection with Agglutination
Authors: Mishulow Lucy , Klein Irving F. , Liss Mildred M. , Leifer Lillian 
Published: January 2023

Summary
A total of fifty-eight serums were tested for protective and agglutinating antibodies—41 serums from 38 typical pertussis cases; 10 from convalescent pertussis donors; and 7 from recovered scarlatinal patients, 4 of whom had a history of pertussis a number of years previously, and 3 had a negative history.
Of the 38 pertussis cases, 30 protected from one-third to all of the mice tested. In one instance the serum gave doubtful protection when tested on the 14th day of the whoop, and became strongly positive when tested 44 days later. In another instance the result was negative when tested on the 6th day of illness and became positive 44 days later. Five patients in this group gave doubtful protection (8 to 20 per cent) and 3 were negative. One of the 3 negative cases had pneumonia at the time of the test and died shortly after; and the other 2 whooped for 10 and 16 days respectively. If we set an arbitrary standard for positive protection as the survival of at least one-third of the total number of mice tested, 78.9 per cent of the typical pertussis cases were positive.
There were 18 patients in this group who gave positive agglutination, but their agglutinin-titers varied within wide limits (10 to 1000+), and did not correspond either to the duration of illness, or to the protective power of the serum (table 3). Serums that were negative or had a low agglutinating power protected as well, and in some instances, better than those that had a high agglutinating power. Thus the protective power of the serums is apparently entirely distinct from their agglutinating power. We found this to be the case in a study of the protective and agglutinating antibodies in antimeningococcus serums (22). There was only one serum in this group that agglutinated in 1:150 dilution but was negative for protection. This patient whooped only 10 days and may become positive on later tests. Of the seven non-pertussis serums tested, six were negative and one gave doubtful protection (10 per cent). One serum in this group was positive for agglutination, but negative for protection.
The results obtained with pertussis convalescent serums showed that there was a wide difference in the protective and agglutinating power not only among different donors, but in the different bleedings of the same donor. One of the 5 donors tested, had a high titer of protective and agglutinating antibodies 15 and 34 days after recovery. Another donor gave strong protection and doubtful agglutination 28 days after recovery; but only doubtful protection and no agglutination 120 days after recovery. A third donor gave partial protection and doubtful agglutination 54 and 117 days after recovery; and two donors (4 and 5, table 4) were completely negative 55 to 105 days after recovery. It seems that the protective antibodies in all probability attain their maximal concentration upon recovery or soon after. They may remain stationary for several weeks; then begin to diminish rather rapidly, and may completely disappear from the circulation in several months.