Figure 4.

High NP/CG ratios are critical for elicitation of hapten- and protein-specific IgG titers in CD18^−/− mice. Eight- to twelve-week-old CD18^−/− (open symbols) and WT (filled symbols) mice were immunized intraperitoneally with 100 μg of NP₂₁-CG/aluM (squares), 10 μg NP₂₁-CG/alum (circles), 100 μg NP₄-CG/alum (triangles), or 100 μg CG/alum (diamonds). (a) Serum levels of anti-NP specific IgG₁ were subsequently detected by ELISA on NP₄-BSA coated ELISA plates and calculated in μg/mL by comparison to IgG₁ standards, as described above. (b) For detection of CG-specific IgG₁, sera obtained by bleeding from tail veins were diluted 1 : 10, and then plated out on CG-coated plates in 1 : 5 dilution steps. Serum titers of anti-CG-specific IgG₁ were determined from the last dilution step where the optical density was still above the background level of the assay. For assessment of the primary immune response, results from sera collected at days 7 and 28 are displayed. Besides, measurements for day 49 are shown, and depict IgG₁ titers representative also for further time points assessed during secondary immune responses. Bars represent the median of each group. *P < 0.05; **P < 0.005. Asterisks used in the key box indicate significant differences for the marked cohorts at all times points shown.