Production of antimicrobial peptides is preserved in aging.

There is an increased susceptibility to infections during elderly, mainly because of the decreased efficacy of adaptive immunity to contain microorganisms. Albeit most of the elderly adults develop this deficiency in adaptive immunity only a minor percentage of them developed recurrent infectious diseases, thus innate immunity represents an important barrier to avoid infections in this group of aged people. Since antimicrobial peptides are important molecules of innate immunity in the study we sought to determine whether healthy aging correlates with a proper antimicrobial production. Our results by ELISA and flow cytometry showed that healthy elder individuals produce significant amounts of both cathelicidin and ß-defensin-2 (hBD-2) comparable with those found in healthy young individuals. Our results suggest that during healthy aging the maintenance of the antimicrobial peptide innate immune response may be responsible for the protection against infectious diseases.

Kinetics and cellular sources of cathelicidin during the course of experimental latent tuberculous infection and progressive pulmonary tuberculosis.

In spite of advances in immunology on mycobacterial infection, there are few studies on the role of anti-microbial peptides in tuberculosis. The cathelin-related anti-microbial peptide (CRAMP) is the only cathelicidin isolated from mice. In this work we investigated the cellular sources and the production kinetics of this molecule during experimental tuberculosis, using two well-characterized models of latent or chronic infection and progressive disease. The lung of non-infected control mice expressed CRAMP at very low levels. In both models of experimental tuberculosis the main cells immunolabelled for CRAMP were bronchial epithelial cells, macrophages and pneumocytes types II and I. After intratracheal infection with a high bacilli dose (H37Rv strain) in Balb/c mice to produce progressive disease, a high CRAMP gene expression was induced showing three peaks: very early after 1 day of infection, at day 21 when the peak of protective immunity in this model is raised, and at day 28 when the progressive phase starts and the immunoelectronmicroscopy study showed intense immunolabelling in the cell wall and cytoplasm of intracellular bacilli, as well as in cytoplasmic vacuoles. Interestingly, at day 60 post-infection, when advanced progressive disease is well established, characterized by high bacillary loads and extensive tissue damage, CRAMP gene expression decreased but strong CRAMP immunostaining was detected in vacuolated macrophages filled with bacilli. Thus, cathelicidin is highly produced during experimental pulmonary tuberculosis from diverse cellular sources and could have significant participation in its pathogenesis.