A temperature of 56°C. maintained for from 2 to 5 hours2 was found to destroy the skin-sensitizing capacity of 23 sera obtained from 18 treated hay-fever patients, without diminishing the so-called inhibiting power of the sera. Numerous titrations, performed upon unheated and heated sera obtained from these ragweed-sensitive subjects before and after administrations of ragweed-extract, indicate that two distinct pollen-combining antibodies existed in the serum of each treated hay-fever patient, whereas only one such agent was present in significant amounts in serum procured before therapy. The following characteristics, suggested by the experiments just described and by the literature on the subject, serve to distinguish the two antibodies.

The skin-sensitizing antibody (atopic reagin): 1) combines with the homologous antigen to elicit a wheal type of reaction in the skin of man and of monkeys (19, 20). 2) It is commonly associated with certain allergic manifestations. 3) It is a naturally occurring factor that cannot be induced experimentally with ease in normal persons although several investigators have reported the development of reagins in man following injections of immune horse serum, insulin, and extracts of orris-root (one case), and round worm, as reviewed by Coca (21). Induced reagins were found in non-sensitive subjects who received egg-albumin parenterally (22) and in allergic persons not previously sensitive to the extract of trichina with which they were subsequently injected (23). Reagins to ragweed-antigen were in no instance induced in the serum of nonsensitive subjects who received ragweed-extract during the present investigation. A different situation obtained, however, in the case of the ragweed-sensitive hay-fever patients, for over half of the “P” sera titrated by the serum-dilution method contained more reagin than was present in the corresponding “A” sera. 4) It is destroyed by a temperature of 56°C. maintained for from 2 to 5 hours or by a temperature of 60°C. maintained for 30 to 60 minutes. 5) When reagin is mixed with dilute antigen in vitro and injected intracutaneously into passively sensitized skin, the resulting wheal is only slightly smaller than that evoked by the antigen alone. 6) Normal skin, passively sensitized with reagin-bearing serum, retains its capacity to respond to the antigen for at least four weeks.

The thermostable antibody: 1) is incapable of sensitizing normal skin, no wheal being elicited by mixtures containing the thermostable antibody and its antigen. In fact, the normal response of cutaneous sites sensitized to the related antigen is curtailed when thermostable antibody is present, due to the inactivation of antigen by the thermostable antibody. 2) It was not detected in the serum of untreated allergic subjects. 3) It can be induced in normal individuals and also in pollen-sensitive persons by injections of pollen-antigen even in relatively small dosage. 4) It is destroyed by a temperature of 60°C. maintained for 24 hours, but loses no potency after being subjected to 56°C. for the same period or to 60°C. for ½ to 20 hours. 5) It rapidly inactivates its antigen even in the presence of reagin. Its potency may be estimated, therefore, by the degree to which it can: a) bind antigen and thus prevent the reaction which promptly occurs when passively or naturally sensitized skin is tested with free antigen, and b) increase the requirement of antigen for the neutralization of a passively sensitized, cutaneous site. 6) It is readily diffusible, disappearing in less than 24 hours from normal skin into which it is injected.

Inasmuch as the thermostable factor, found in “P” serum and in the serum of normal individuals following inoculations of ragweed-extract, was induced by parenteral administrations of the ragweed-antigen and reacted specifically in an observable way with that antigen, this agent is an antibody according to the definition of Topley and Wilson (24).

1

Presented at the Fifteenth Annual Meeting of the Society for the Study of Asthma and Allied Conditions at Atlantic City on April 29th, 1939.

2

Since the completion of these experiments, further studies have revealed that a temperature of 60°C. maintained for from 30 to 60 minutes serves more conveniently to destroy the reagin without diminishing the antigen-binding power of “P” sera.

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