Regulation of secondary antibody responses in rodents. II. The requirement for continued antigen supply to maintain IgG production.

The regulation of secondary antibody production in mice is studied in adoptive transfer experiments. Mice immunized twice with chicken red blood cells (CRBC) in Freund's complete adjuvant (adjuvant) at 28 day intervals subsequently produce high levels of IgG anti-CRBC antibody for several weeks. Immunization with CRBC in saline also induces prolonged splenic production of IgG anti-CRBC antibody but at a much lower level. It was not possible to augment the level of antibody production in mice immunized with CRBC in saline by transfer of very large numbers of spleen cells from mice immunized with CRBC in adjuvant. Transfer experiments in the opposite direction failed to suppress antibody responses in mice immunized with CRBC in adjuvant. Similar experiments were carried out with mixed transfers into third party non-immune irradiated recipients. The requirement for continued antigen supply to maintain secondary antibody production was shown in that IgG anti-CRBC antibody production in non-immune recipients of immune spleen cells ceased within five days when the recipients were not given antigen. It is concluded that: (i) while strong regulation of secondary antibody production against CRBC exists, this is not a function of transferrable suppressors; (ii) increased antibody production in animals treated with adjuvant is not due to increases in the number of antigen-sensitive T or B lymphocytes; and (iii) the data are most easily explained by a hypothesis which implicates the rate of triggering of lymphocytes as the regulatory step in secondary antibody production. This could be a factor relating to the supply of antigen or the number of sites in secondary lymphoid tissue at which antigen can trigger.