Cathelicidin gene expression in porcine tissues: Roles in ontogeny and tissue specificity

Cathelicidins constitute a family of mammalian antimicrobial peptides chat are synthesized in the bone marrow as prepropeptides, stored in neutrophil granules as propeptides, and released as active, mature peptides upon neutr ophil degranulation. We investigated the developmental expression of two po rcine cathelicidins, PR-39 and protegrin. Both cathelicidins were expressed constitutively in the bone marrow of all pigs at all of the ages tested. P eripheral blood neutrophils from young pigs expressed PR-39 and protegrin m RNA, which were not detectable at 42 days of age. At earlier ages, expressi on of PR-39 mRNA was detected in the kidney and liver and several lymphoid organs, including the thymus, spleen, and mesenteric lymph nodes, but disap peared at 4 weeks of age. These data provide the first evidence of cathelic idin gene expression in peripheral leukocytes and may indicate a role for t hese antimicrobial peptides in the development of host defense mechanisms.