Figure 3.
(A) Binding of intact TNP-specific IgG2a (7B4) (solid symbols) and F(ab′)2 prepared from 7B4 (open symbols) to BSA-TNP in ELISA. Twofold serial dilutions were started with antibody preparations containing 32 hemagglutination units (HU)/ml [corresponding to 68 μg/ml 7B4 and 272 μg/ml of F(ab′)2]. (B) Groups of four to five (C57BL/6 × DBA/2)F1 mice were immunized with 1 × 106 SRBC-TNP and 4 × 105 HRBC preincubated for 1 hr at 37°C with the indicated amounts of intact TNP-specific IgG2a (7B4) (solid symbols), F(ab′)2 of IgG2a (7B4) (open symbols), or PBS. The antibody preparations were the same as those tested in A. Mice were given 54 (containing 6.4 HU), 10, 1, or 0.1 μg F(ab′)2 and 10 (containing 4.7 HU), 1, or 0.1 μg intact 7B4. Five days later the direct SRBC-specific (solid line) and HRBC-specific (broken line) PFC/spleen were assayed. PFC/spleen in the respective control groups (receiving antigen alone) were: 22,368 SRBC; 26,701 HRBC. This experiment was repeated twice: once with a single dose in (C57BL/6 × DBA/2)F1 mice and once as a titration in C57BL/6, with both experiments giving similar results. (C) Groups of three to five (C57BL/6 × DBA/2)F1 mice were immunized with 4 × 106 SRBC-TNP and 8 × 105 HRBC preincubated with 0–50 μg of IgE anti-TNP (IGELb4) (solid circles) or IgG2b anti-TNP (1B4) (open circles). Five days later the direct SRBC-specific (solid line) and HRBC-specific (broken line) PFC/spleen were assayed. PFC/spleen in the respective control groups (receiving antigen alone) were: 41,400 SRBC; 32,289 HRBC. In another experiment, mice were immunized with 50 μg IGELb4 or two other monoclonal TNP-specific IgE antibodies (IGELa2, IGELb1) and SRBC-TNP. All three IgE antibodies induced more than 90% suppression (not shown).