Genetics of the immune response. I. The immune response to the phage fd in high and low responding inbred strains of mice

The immune response to the bacteriophage fd has been analyzed in several inbred strains of mice. The inactivation curve of bacteriophage fd by specific antisera follows initially first order kinetics and finally levels off gradually. The strength of the antisera has been characterized primarily by the velocity constant K of the inactivation kinetics. Two other methods, endpoint and plateau determination, have been used for the analysis of selected problems. The threshold dose for priming for a secondary response varies widely among the strains tested. Low responding strains have a hundred‐ to thousandfold higher threshold dose than high responding strains. High responsiveness is dominant over low responsiveness in genetical analysis and inherited as a single dominant trait. The dose for an optimal response in high and low responders lies within the same range at about 1 × 109 fd/g body weight. Further increase of the priming dose leads in all except one strain to a suppression of the response probably due to partial high zone paralysis. One strain of mice, CBA/MH, shows a dose response curve different from the others. No suppression of the response with high priming doses is found. The cooperating role of thymus derived cells and of macrophages has been tested. The previous uptake of antigen by macrophages probably prevents induction of high zone paralysis. No evidence has been found for macrophages being responsible for high and low responsiveness. The immune response to phage fd is strongly thymus dependent. The response of animals lacking thymic influence is below the response of low responders.