Occurrence of Schick Negative Reactions in Absence of Free Antitoxin in Blood Stream.

Abstract

The object of this communication is to present some observations concerning the relationship of antitoxic immunity to the Schick test.

The Schick test, consisting of the intra-dermal injection of 1/50 M. L. D. of diphtheria toxin, shows under proper conditions, a reaction at the site of injection in the non-immune (positive), and a complete absence of reaction in those who are immune (negative). The generally accepted explanation of a negative Schick test is that antitoxin is present in the blood serum, the circulating antitoxin reaching and neutralizing the toxin before tissue damage results.

This explanation is of course plausible, especially since we know of no product of the tissues capable of neutralizing toxin, except antitoxin. There was no ground for dispute of this hypothesis, so long as the presence of antitoxin in the blood was predicated, but it now develops as a result of a series of comparative observations with the Schick and the Kellogg 1 tests that there are individuals who give absolutely conflicting results, in that a negative Schick is accompanied by a lack of antitoxin in the blood as shown by the Kellogg test. These persons have all, with one exception, been found in the group of those originally Schick positive and who have become Schick negative by the administration of toxin-antitoxin. This may have a bearing on the explanation of the phenomenon, and points the way toward a line of investigation.

Attention was first directed to this matter, when some children in the California School for the Deaf and Blind, who had been immunized and later found to be Schick negative, were inadvertently included in a group that was having blood samples taken for the Kellogg test.