Research Note: Intestinal avian defensin 2 and robustness of chicks

Abstract

Poultry production is an important agricultural sector for human food worldwide. Chicks after hatch often face health problems leading to economic losses that are deleterious for breeders. Avian defensin 2 (AvBD2) is a prominent host defense peptide of the intestinal mucosa of cecum and is involved in the resistance of poultry to bacterial pathogens. This peptide could thus represent an innate immunity marker of robustness of birds. To test this hypothesis by comparing fast-growing and slow-growing lines in different conditions of breeding, the chick's cecal AvBD2 content was analyzed according to animal quality and immunity indicators. Chick's cecal tissue sections labeled by immunohistochemistry with newly developed specific antibodies revealed the localization of AvBD2 in the mucosa with high individual variability, without showing differences attributable to quality indicators, but interestingly showing inverse correlation with seric IgM levels in the fast-growing line. The availability of our anti-AvBD2 antibodies to the scientific community opens perspectives to identify the cellular sources of this defensin in the cecal mucosa and to investigate the organization and function of innate immune arsenal of birds.

Keywords: chick; defensin; intestinal immunity.

Figure 1

IHC analysis of AvBD2 in cecal tonsil from a representative S chick (top) and from a representative L chick (bottom). Left panels (A, D): normal rabbit Ig used as primary antibody negative control; Right panels (B, C) and (E, F): rabbit anti-AvBD2 polyclonal antibodies; Peroxidase conjugate goat anti-rabbit Ig was used as secondary antibody. Images were analyzed by Image J (Fiji) software to quantify percent area of the tissue section stained for AvBD2 (%S+), as indicated at the top of panels B and E. V: villus; C: crypt; M: muscle; L: lumen.

Figure 2

Scatterplot representation of seric IgM concentration as a function of % AvBD2 positive area of cecal tonsil tissue. Values from line L chicks are in blue (n = 10) and values from line S chicks are in orange (n = 10). For line S chicks, linear regression is in dotted line whose equation as well as Pearson's correlation coefficient r and P values are indicated.