Suppression of the adaptive immune response after non-specific immunization.

<p>(A, B) NSI alone did not induce OVA-specific serum antibodies but increased total serum IgG. OVA-specific IgG (A) and total serum IgG (B) were measured 21 days after NSI (n = 3). Animals without NSI and immunization (n = 3 and 6), only immunized animals (n = 5 and 11), and animals immunized 7 days after NSI (n = 6 and 11) served as controls. (C, D) NSI reduced the specific response to antigen priming. C57BL/6 mice were non-specifically immunized (NSI, adapted from [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0192197#pone.0192197.ref029" target="_blank">29</a>]). At the indicated time points after NSI, the animals were primed intraperitoneally with TNP-OVA/OVA in alum (n = 5–6). Animals without NSI and immunization (n = 6) and animals immunized without prior NSI (n = 5) served as controls. The antigen-specific immune response was measured as the concentration of anti-OVA IgG in the serum 14 days after priming with OVA by an ELISA. (C) The relative concentrations of OVA-specific IgG antibodies in serum normalized to a standard serum (arbitrary unit, AU) are shown. (D) The relative antibody affinity of TNP-specific IgG was measured as binding to slightly haptenized TNP-BSA in comparison to highly haptenized TNP-BSA in an ELISA (adapted from [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0192197#pone.0192197.ref034" target="_blank">34</a>]). (E) The NSI-induced immune suppression was independent of CpG. C57BL/6 mice were treated with NSI containing CpG (NSI, n = 12) or not (NSI w/o CpG, n = 6). Seven days later, they were immunized intraperitoneally with TNP-OVA/OVA in alum (OVA). Mice without NSI and immunization (n = 7) and animals immunized only (n = 9) served as controls. The antigen-specific immune response was determined as described for panel C. In the panels A-D means and 95% confidence intervals are shown. Kruskal-Wallis test and Dunn’s multiple comparison for selected pairs. In panels B and E pooled results from two separate experiments are shown. *** P <0.001; * P <0.05.