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Studies on antibody induction in vitro. II. Cellular requirements for a primary response to soluble T2 antigens by rabbit cell cultures.

The primary in vitro response of cultured rabbit spleen cells to solubilized T2 phage (S-T2) was used to study the cellular requirements for immune in-induction. Rabbit lymph node cells, in contrast to spleen cells, were found not to respond to S-T2, and the addition of spleen cells insufficient in number to give rise to antibody in themselves failed to supply a missing cell type to lymph node cell cultures. The period in culture during which antibody formation by spleen cells could be induced was shown to be transitory, in that addition of S-T2 even 24 hours after culture initiation resulted in little, if any, antibody production. Cultures of non-adherent cells from spleen, obtained by removal of adherent cells on plastic dishes or glass bead columns, by silica treatment for removal of phagocytic cells, or by sequential treatment by adherence and with silica, responded as well to S-T2 as did the whole spleen cell population. These findings strongly indicate the relative macrophage independence of the in vitro response to S-T2 and are suggestive of the role of macrophages in solubilization of antigens, since intact phage fails to induce antibody formation in macrophage-deprived cultures.