Competition for antigen by cell populations having receptors with the same specificity but of different idiotype.

All normal A/J mice immunized with keyhole limpet hemocyanin-p-azophenylarsonate (KLH-Ar) produce anti-Ar antiboides, some of which share a cross-reactive idiotype. The present results indicate that the biosynthesis of antibody molecules bearing this idiotype does not occur in mice having an excess of lymphoid cells with receptors for Ar that lack the idiotype. This was shown, first, by introducing into normal, nonirradiated mice lymphoid cells from mice which had been suppressed with respect to production of the idiotype and then immunized with KLH-Ar. The recipients failed to express the idiotype upon immunization. Alternatively, cells from suppressed, mice were transferred into lethally irradiated syngeneic recipients, followed 17 days later by normal cells. All recipients expressed the idiotype upon immunization. If, however, the recipients were challenged with antigen between the two cell transfers, antibodies bearing the idiotype were not produced during subsequent immunization. Arguing against active, cell-mediated suppression was the production of the idiotype by normal cells in the presence of cells from a suppressed animal. However, the possibility of active suppression by hyperimmune suppressed cells was not ruled out. On the basis of the present data, the simplest interpretation is that cells with anti-Ar receptors from immune, suppressed animals, being present in larger numbers, compete successfully for antigen with nonimmune cells and thus prevent the expression of the idiotype. The system may provide a basis for quantitative studies of competition among cells for a limited supply of antigen, particularly if B cell populations are utilized.