Complexity of the Scarlet Fever Toxin and Antitoxin
Authors: Park William H. , Spiegel Rose Goldschmidt 
Published: December 2022

Summary and Conclusions
The fact that an individual convalescent scarlet fever serum neutralizes the toxin of a certain scarlet fever streptococcus in certain susceptible persons and not in others proves that the toxic filtrate has more than one toxin and that a person may be susceptible to one component and not to another or others. We can conceive that the usual scarlet fever strain makes a toxic filtrate containing the different toxins A, B, C, D. A less common strain A, C, D, E or B, C, D, E. Strains from some septic sore throats C, D, H, I and from some erysipelas cases C, D, K, L. Antitoxins to a greater or less degree would develop in any person or animal injected with any toxic filtrate to neutralize the actual toxins present in the filtrate.
The finding that a certain convalescent serum or antitoxic horse serum will fail to neutralize a toxin for certain persons in the same quantity which is successful in others, but in larger amount succeeds, proves that the antitoxic response is different for the different component toxins either because of the different proportions of the toxins in the filtrate or because the child or animal responds differently in degree to the stimulus of the different toxins. We have the analogy of horses receiving the same amount of diphtheria and tetanus toxin. Some produce strong antitoxin for diphtheria but weak for tetanus and others strong antitoxin for tetanus but weak antitoxin for diphtheria.
A convalescent scarlet fever serum from a single patient may fail to cause blanching in a true case of scarlet fever because the two cases are due to two strains that differ in at least one toxin and so in one induced antitoxin. It is also probable that there are strains of streptococci that have the power to produce scarlet rash producing toxins which are quite different from the standard Dick strains, so that after convalescing from infection due to one strain a second infection might occur from the other strain. Every year a few cases sent into the hospital with the diagnosis of scarlet fever after recovery develop a second attack. We have been inclined to think that the first attack was not scarlet fever while if we had made a culture, we possibly would have found a strain of streptococci that made different toxins from the usual cases. If this assumption is true a case of scarlet fever at the onset might give a negative Dick test to the Dick strain toxin and its serum would then neutralize the standard toxin and blanch the rash of an ordinary case of scarlet fever. The point is that it is not safe at the present time to limit the diagnosis of scarlet fever to cases due to the usual strains making the standard group of toxins. At most the exceptional strains cause only a small minority of the cases of scarlet fever. Cases that do not respond to the serum should be studied carefully to determine whether their strains are typical ones. It is possible that in these a polyvalent antitoxic serum is indicated or it may simply be that the scarlet fever streptococci or other streptococci or other microorganisms have invaded the deeper tissues and are beyond the help of antitoxins. Further investigation is necessary to determine the value of a bactericidal serum in these cases.