A persistent IgE anti-hapten antibody response was established by immunization of B6D2F1 mice with a minute dose of aluminum hydroxide-gel-absorbed dinitrophenyl-keyhole limpet hemocyanin (DNP-KLH) or DNP-ovalbumin (OA). Irradiation of the immunized mice with a lethal dose of X-rays suppressed secondary anti-hapten antibody responses to DNP-homologous carrier conjugate, and depleted hapten-primed B memory cells in their spleen. However, persistent antibody formation of both IgE and IgG isotypes in the immunized mice was not affected by the lethal dose of X-rays. The results indicated that recruitment of B memory cells to antibody-forming cells is not responsible for the maintenance of antibody levels. The hapten-primed B cell population was expanded by adoptive transfer of DNP-KLH-primed spleen cells into irradiated mice followed by challenge with homologous antigen. Culture of T-cell-depleted spleen cells of the recipients, in the absence of exogenous antigen, resulted in the production of both IgE and IgG anti-DNP antibodies. The antibody titer in the culture supernatants continued to increase for 14 days, indicating that long-lasting antibody-forming cells are present in the spleen. The antibody-forming cells are radioresistant. The in vitro production of IgE anti-DNP antibodies by the spleen cells was not affected by the presence of IgG anti-DNP antibody, but was inhibited by exposure of the cells to multivalent DNP-heterologous carrier conjugates, such as DNP-bovine IgG (BGG) or DNP-mouse IgG (MGG). The persistent anti-hapten antibody formation of DNP-OA-primed and irradiated mice was depressed by an injection of DNP-MGG, which induced secondary anti-hapten antibody responses in the antigen-primed and nonirradiated mice. The results support the concept that radioresistant long-lived antibody-forming cells are involved in persistent antibody formation in the irradiated mice.
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