Promotion of anti-keyhole limpet hemocyanin IgM and IgG antibody productions in vitro by red bell pepper extract

Red bell pepper (Capsicum annuum L.), eaten as vegetables, is a rich source of vitamin C and E, provitamin A, β-carotene, and numerous phenolic compounds. Its antioxidant, anti-mutagenic and anti-inflammatory properties have been reported. However, scientific report on its immunomodulatory activities is scarce. We, for the first time, reported the promotion of polyclonal immunoglobulin (Ig) M production by red bell pepper extract (RBPE). The present study was aimed to investigate the activity of RBPE on keyhole limpet hemocyanin (KLH)-specific IgM and IgG antibody productions in vitro. Anti-KLH antibodies, anti-KLH IgM secreting cells, and viable cells were determined by ELISA, ELISPOT and MTT assays, respectively. RBPE (0.75 and 1.5 mg/mL) significantly enhanced the production of anti-KLH IgM in cultured splenocytes of non-immunized (189 and 184%, respectively) and immunized mice (145% at 1.5 mg/mL). The same doses promoted the formation of anti-KLH IgM secreting cells 185 and 232%, respectively. Moreover, RBPE (0.375 mg/mL) augmented anti-KLH IgG production by 145 and 157% in cultured splenocytes collected from mice 1 and 3 weeks after a booster injection. Thus, RBPE induced KLH-specific antibody productions. The findings of the present study suggest that consumption of RBPE or vegetables may be beneficial to strengthen humoral immune responses.