Modulation by Bovine Lactoferrin of Parameters Associated with the IgA Response in the Proximal and Distal Small Intestine of BALB/c Mice

Background: Secretory IgA (SIgA) and the polymeric immunoglobulin receptor (pIgR) have a pivotal role in gut homeostasis. Bovine lactoferrin (bLf) has been shown to modulate intestinal immunity and endogenous corticosterone. Considering the regionalization of the intestinal immune response, the aim of this work was to compare the impact of bLf on the IgA response in the proximal versus distal small intestine under physiological conditions.Methods: Groups of healthy male BALB/c mice were orally treated with one daily dose of bLf (50, 500, or 5000 mu g) or untreated (control) for 7 d, and then sacrificed. From plasma samples, corticosterone levels were determined by an enzyme-linked immunosorbent assay (ELISA) kit. From distal and proximal segments of the small intestine, the following material was obtained: intestinal secretions to evaluate IgA levels by ELISA; epithelial cell extracts for protein-analysis of alpha-chain and pIgR by Western blot; mucosa samples for mRNA analysis of alpha-/J-chain, pIgR, and interleukin (IL)-2, -4, -5, and -6 by real-time quantitative reverse transcription polymerase chain reaction (RT-PCR).Results: With 5000 mu g of bLf, there were greater modulatory effects in the distal (versus proximal) segment, evidenced by an increase in the (i) level of total and specific IgA, (ii) protein expression of alpha-chain and pIgR, (iii) mRNA transcripts of alpha-chain, IL-2 and IL-5, and (iv) level of plasma corticosterone.Conclusions: Endogenous corticosterone elicited by bLf may have allowed for an IL profile that favored the IgA antibody response. The latter has a key role in maintaining intestinal homeostasis.