Idiotypic specificities of rabbit anti-Salmonella abortus-equi antibodies produced by spleen cell clones involved in successive transfers in irradiated rabbits

Abstract

Rabbits irradiated with 750 rad were reconstituted with different amounts of spleen cells from the same donor previously immunized against Salmonella abortus-equi (S. a. e.). Two limited numbers of spleen cell clones producing anti-S. a. e. antibodies were respectively expressed in two recipients of the smallest amount (5 x 10(6)) of donor spleen cells. We tried to propagate these spleen cell clones in two new sets of irradiated recipients. We prepared antiidiotypic sera with the anti-S. a. e. serum of respectively (1) the initial donor of the cells, (2) the two intermediate recipients in which a restricted number of spleen cell clones were expressed and (3) one rabbit from each of the second two sets of recipients in which it seemed, as judged by the anti-S. a. e. antibody spectrotypes, we succeeded in propagating these spleen cell clones. With these antiidiotypic sera, we looked for the spleen cell donor idiotypes in the anti-S. a. e. serum of the diverse recipients and vice versa. Recipients of 1 x 10(8) or 2.5 x 10(7) spleen cells produced anti-S. a. e. antibodies with a spectrotype as heterogeneous as the spectrotype of antibodies produced by the donor. These antibodies carried the idiotypic pattern of the donor's antibodies, which was revealed by a given antiidiotypic serum, and the donor's allotypic patterns. The two recipients of 5 x 10(6) spleen cells which were used as intermediate spleen cell donors for the two new sets of irradiated rabbits produced antibodies of restricted heterogeneity which carried donor's allotypic patterns but not the idiotypic pattern of the donor's antibodies (revealed by a given antiidiotypic serum). We observed during these two successive spleen cell clone transfers the expression, in the irradiated recipients, of several idiotypes of anti-S. a. e. antibodies which were not detected in the anti-S. a. e. serum of the spleen cell donor and sometimes even not in the anti-S. a. e. serum of the intermediate donor. The antibodies we studied were produced by the donor's spleen cells as they carried donor allotypic patterns and came from bleedings made one week after transfer, a time which is not sufficient for irradiated rabbits used as controls to recover their aptitude to mount an antibody response after the damages caused by the irradiation. Presumably, spleen cell clones which did not produce antibodies in the donor were recruited to produce antibodies during the successive transfers. These spleen cell clones might have been kept silent in the donor by the clonal dominance phenomenon, this dominance being broken or totally changed during the transfers.