Studies on the control of antibody synthesis. VII. Change in affinity of direct and indirect plaque-forming cells with time after immunization in the mouse: loss of high affinity plaques late after immunization.

The change in avidity of anti-hapten antibody with time after immunization was studied in mice at the level of the antibody-forming cell. A progressive increase in avidity was seen in both direct and indirect plaque-forming cells. Late (38 days) after immunization with a large dose of antigen there was a preferential loss of high avidity plaque-forming cells and the average avidity decreased. High avidity memory cells were still present since boosting resulted in the prompt appearance of very high avidity plaque-forming cells. There was a strong positive correlation between the avidity of the direct and the indirect plaque-forming cells present in the same spleen. A pattern of change in avidity and heterogeneity of avidity similar to that observed with intact animals was seen in lethally irradiated mice reconstituted with normal spleen and thymus cells.