The adoptive secondary response to human serum albumin under conditions of high antigen pressure. The response of high and low avidity B cell subsets.

Thoracic duct lymphocytes (TDL) from (AS2 x AS)F1 rats previously injected with human serum albumin (HSA) were transferred to 900 r irradiated syngeneic recipients which were challenged with various doses of soluble HSA (s-HSA). TDL from partially tolerant rats, which were deficient in high avidity B cells, produced a maximum PFC response to the largest challenge dose (1 g s-HSA). In contrast, high avidity B cells from primed donors were optimally stimulated by 1 microgram and maximally inhibited by 1 mg s-HSA (day 7 PFC). An additional increase in antigen concentration by 1000 fold failed to diminish the PFC numbers further. Plaque inhibition profiles indicated that these antibody forming cells resisting inhibition were of the same high avidity as those triggered by low doses of antigen. The inability of s-HSA to completely inhibit antibody synthesis is discussed with regard to current views on B cell inactivation. Evidence is also presented which indicates that the standard haemolysis-in-gel test may fail to detect many low avidity antibody forming cells to proteins.