Antigens in immunity. VII. Analysis of immunological memory.

Rats were given primary and secondary injections in saline solution without adjuvants, of flagellar antigens, the dose varying from 10 pg (10g) to 1 mg. Rats were bled at various times after injection, and levels of both total (7S+19S) and mercaptoethanol resistant (7S) anti-H antibody were determined, using a serial two-fold dilution assay. The data from several thousand such titrations was entered on IBM punched cards and a series of programs were written to allow computer analysis thereof. The chief findings which emerged from the study were: (1) Important differences exist in the kinetics of primary and secondary responses. (2) The excess antibody formation characteristic of the secondary response is essentially a short-lived phenomenon. (3) Conditions may be defined for the demonstration of excellent secondary responses where the additional antibody formed is solely 19S. (4) Secondary responses are evoked only when the second dose of antigen equals, or preferably exceeds, the first dose. (5) Peak antibody titre: antigen dose curves differed for primary and secondary responses. (6) Memory can be quantitated in a variety of ways. The hypothesis that memory stems from a series of cellular events induced by antigen but independent of actual antibody formation is discussed. (7) Optimal conditions for the study of the role of antigen in the secondary response were established.