Mechanism of B-Cell Activation and Paralysis by Thymus-Independent Antigens

Normal spleen cells showed a bell-shaped dose response profile when stimulated in vitro with die thymus independent antigen (4 -hydroxy-3,5 dinitiophenyl)acetyl (NNP)-lipopolysaccharide (LPS) with regard to the development of high-avidity plaque-forming cells to NNP The addition of suboptimal concentrations of LPS to cultures stimulated by suboptimal concentrations of NNP LPS resulted in optimal induction of B cells in that affinity fraction Addition of LPS to cultures optimally stimulated by NNP-LPS resulted in paralysis of the specific cells These results are interpreted in terms of the additive effects between the mitogenicity LPS and the mitogenicity of NNP LPS the latter being selectively focused on the specific cells, thus providing further evidence for the 'one nonspecific signal' hypothesis for immune activation of B cells