Letter from Michael Heidelberger to Simon Flexner, Rockefeller Institute for Medical Research
In this letter to his former boss, Heidelberger critically reviewed experimental evidence on the use of antiserum to type
III pneumococcus presented by Hugh K. Ward, an immunologist at Harvard University Medical School, in the Journal of Experimental
Medicine, vol. 55 (1932). Ward had argued that type III antipneumococcus serum, after absorption with the specific carbohydrate
of the pneumococcal capsule, no longer formed a precipitate with the carbohydrate, but nonetheless retained a definite, though
diminished bactericidal effect on virulent pneumococci in a bactericidal test. He asserted that this carbohydrate neutralization
test was a much more delicate method for detecting the anticarbohydrate antibody (precipitin) than the precipitin test, the
type of test Heidelberger and Kendall had used in their quantitative studies of antibody-antigen reactions. Heidelberger
charged that Ward's conclusions resulted from methodological and mathematical errors.
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1932-04-21 (April 21, 1932)
Rockefeller Institute for Medical Research
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Medical Subject Headings (MeSH):
Antigens and Antibodies: Heidelberger and The Rise of Quantitative Immunochemistry, 1928-1954
Letter from Simon Flexner, Rockefeller Institute for Medical Research to Michael Heidelberger (May 2, 1932)
While I cannot presume to elucidate Ward's paper for you, as you suggest, I did hope you would be willing to hear my criticism
of it, based on the quantitative studies Kendall and I have made.
In calculating that 200 cc. of type I antiserum would take care of 500 gm of S, or the amount in 12,500 liters of culture,
Ward has forgotten entirely that S will be "functionally" in excess as soon as it exceeds the amount which can combine
chemically with the antibody of the serum. Our work has shown that when S begins to be in excess its ratio to combine antibody
is 1:60. Now a type I antiserum of 1000 mouse protective units contains about 7 mg of specifically precipitable protein per
cc. (Ref. 8 in Ward's first April paper) and 200 cc. would contain 1400 mg. Therefore, as soon as 1400/60 or 23 mg. of
S had combined with the antibody the serum would be useless and the rest of any S present would be actually in excess and
free to "function" antibacterially. Since this amount corresponds roughly to that in one-half liter of culture, not
12,500 l, it is easy to understand why large amounts of serum must be given, and given early, to be of any value. And since
virulent Type 3 organisms produce at least 2.5 times as much S as type I does, 200 cc. of an equally good 3 antiserum would
neutralize the S produced by only 200 cc. of culture, so that the inadequacy of type III antiserum is thus very satisfactorily
account for, as well.
As for the bactericidal effect of serum absorbed with polysaccharide, I cannot believe that 10 percent of free anti-carbohydrate
can be left behind, as we have quantitative measurements indicating that the amount must be almost infinitesimal. A possible
explanation is that the small amount of AS2 (completely neutralized antibody) remaining in solution can combine at the surface
of the Pn III with S (we have given evidence for an AS3 compound) and thus prepare the organism for phagocytosis by the blood
used in Ward's test. So-called protective antibodies remaining after absorption with S could be accounted for in the
As for the enhanced antibactericidal effect of a Pn III filtrate over that of a corresponding amount of pure S III, Ward's
data do appear to show a 100-fold, not a 1000-fold increase, and while the cause of this my lie in a more reactive intermediate
product, a part of the discrepancy, at least, may be traceable to too great reliance on the quantitative interpretation of
a complete qualitative test which may, in the end, turn out to be an artifact.
Nina and I enjoyed the tea enormously and had hoped to tell you and Mrs. Flexner so at last night's very thrilling concert.
With many thanks for your patience in letting me send this criticism,