Immunization.

The mice were intraperitoneally (i.p.) injected with 10 μg NP₁₀-LPS or with 100 μg NP₂₁-KLH in alum. Serum was collected before, 1 week after (NP-LPS), and 4 weeks after (NP-KLH) immunization. NP-specific Ig titers were determined using Nunc Maxisorb plates coated with 50 μl per well of 5 μg/ml NP₂‐bovine serum albumin (BSA) or NP₁₄/NP₁₆-BSA, and horseradish peroxidase (HRP)‐labeled goat anti-mouse IgM, IgG1, IgG2, or IgG3 antibodies (Southern Biotech, 5300-05). For quantification, reference wells were coated with goat anti-mouse Ig capture antibody and purified mouse IgM, IgG1, IgG2, or IgG3 (Southern Biotech, 5300-01). Enzyme-linked immunosorbent assay (ELISA) plates were developed using 2,2'-azinobis(3-ethylbenzothiazolinesulfonic acid) (ABTS) and read using a Polarstar at 410 nm.