Differential localization of lingual antimicrobial peptide in the digestive tract mucosal epithelium of calves.

Immunolocalization of lingual antimicrobial peptide (LAP), a member of the β-defensin family, in the digestive tract of calves was investigated to determine its distribution in the digestive tract of Holstein-Friesian calves. Various regions of the digestive tract were collected from slaughtered calves, and fixed in 10% formalin in PBS. Paraffin sections were stained with anti-LAP antibody, followed by visualization of immunoreactions products utilizing the avidin-biotin complex method. Expression of LAP mRNA was analyzed with reverse transcription-PCR. Immunoreactive LAP was localized in the stratum corneum of the stratified squamous epithelium of the tongue, esophagus, rumen, reticulum and omasum but not in their basal layer and lamina propria. In the gastric glands of the abomasum, only chief cells showed LAP positive reaction at the apical side of their cytoplasm. Lamina propria and Peyer's patch of the ileum had some leukocyte-like cells immunopositive for LAP. Weak immunoreaction of LAP was also detected in the mucosal epithelium of the intestinal gland of the cecum, colon and rectum. All regions of digestive tract showed LAP mRNA expression with PCR. These results indicate differential localization of LAP in the mucosal epithelium of digestive tracts in calves. The LAP expressed in stratum corneum of stratified squamous epithelium and chief cells of abomasum specifically may play role in the innate immune function in these tissues.