Differences in Primary and Secondary Immunizability of Inbred Mice Strains

Abstract

Immunizability is defined in terms of amount of a given antigen that is necessary to confer a defined degree of immunity. Pure inbred mice strains were found to differ up to 10-fold in respect to primary immunizability, referring to immunity after one dose of tetanus toxoid. The same strains were tested with two doses of toxoid separated by various time intervals. Whatever the time interval, the strains differed in respect to the amount of the first dose necessary to confer immunity, and the order of immunizability found after two doses correlated with the primary immunizability. Although the regression of response on the first dose increased with time interval and was independent of strains, the regression of response on the secondary dose was independent of time—the flatter, the better immunizable the strain. Mean responses for the same set of doses showed a regular linear increase over three weeks. The results are interpreted in the light of current hypotheses on antibody production. Differences in immunizability are explained as differences in the ease and speed with which cells are first matured into specific antibody production cells whereas the rate of multiplication of these cells bears little or no relation to immunizability.