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Immunoglobulin synthesis by thymus B cells.

Rabbit lymphoid cells transferred to newborn recipients synthesized donor-type immunoglobulin. Elimination of donor T cells did not affect this synthesis of donor immunoglobulin, while elimination of B cells abolished or significantly decreased the synthesis. The synthetic capacity of B cells from thymus was thirty-four times greater than the synthetic capacities of B cells from spleen, fifty-five times greater than that of mesenteric lymph nodes and 180 times greater than that of appendix cells. Synthetic activity of spleen cells ceased before the tenth day after transfer, while thymus cells might continue to synthesize immunoglobulin for a longer time. This was shown by comparing half-lives of donor immunoglobulin in the recipients' sera. Increasing the number of injected spleen cells (from 2 x 10(6) to 120 x 10(6)), resulted in a corresponding increase in donor Ig synthesis. With thymus cells, donor immunoglobulin increased with cell numbers up to 2 x 10(7) cells, above this dose there was no further donor immunoglobulin increase in the recipients' serum.