Enhancement of anti-OVA IgG2c production in vivo by enalapril

Abstract

Angiotensin-converting enzyme (ACE) inhibitors have non-hemodynamic, pleiotropic effects on the immune response. The effects of ACE inhibitors on the production of cytokines and T-cell functions are well established. However, little is known on the effects of these medicines on humoral response to foreign antigens. In this study, we investigated the effect of enalapril treatment on ovalbumin (OVA)-specific IgG1 and IgG2c production in mice determined by ELISA. Two groups of 8-week-old C57BL/6 females mice (3-4/group) were subcutaneously immunized with OVA (10 μg/animal) in presence of Alhydrogel (1 mg/mouse) and boosted at day 21. The mice were treated with enalapril (5 mg/kg daily, po) or were left without treatment for one month. The animals were bled from the orbital plexus on days 0, 7, 14, 21, and 28 after the first immunization and the sera were stored at -20°C until usage. OVA-specific serum IgG1 and IgG2c were determined by ELISA using serum from each individual animal. The results showed that enalapril significantly increased anti-OVA serum IgG2c in the secondary response without affecting IgG1 synthesis. These data expand our understanding on the properties of enalapril on the immune response, including antibody production.

Figure 1. Evaluation of the effect of enalapril (EP) on ovalbumin (OVA)-specific IgG1. Two groups of mice (3-4/group) were subcutaneously immunized with OVA/Alhydrogel (Al) and boosted at day 21. The mice were orally treated with enalapril or were left without treatment. OVA-specific IgG1 was determined by ELISA using 1:400 diluted serum. Data are reported as means±SD and represent 2 independent experiments.

Figure 2. Levels of anti-ovalbumin (OVA) IgG2c during the study period. Two groups of mice (3-4/group) were subcutaneously immunized with OVA/Alhydrogel (Al) and boosted at day 21. The mice were orally treated with enalapril (EP) or were left without treatment. OVA-specific IgG2c levels were determined by ELISA using 1:1000 diluted serum. Data are reported as means and represent 2 independent experiments. *P=0.0006, one-way ANOVA followed by the Tukey's test.