ABSTRACT
PURPOSE: Despite the high prevalence of respiratory diseases in the world and the extensive information available on the mucosal immune system, research on the development of the lung immune system in humans is limited by technical and ethical considerations; therefore, we studied the postnatal development of T lymphocytes in lung lobes in a porcine model. METHODS: Using less than 36-hour-old (NB), 1-week-weaned (5-week-old -AW-), 3-month-old (3M), and 4-year-old (4YR) healthy, nonvaccinated, specific pathogen free (SPF) Vietnamese miniature pigs, we studied the CD3+, CD4+, CD8+, TCR1 (gamma-delta T cells), and CD25+ (IL-2R-alpha) cell subpopulations in lung lobes parenchyma, bronchoalveolar lavage (BAL), peripheral blood mononuclear cells (PBMC), and cervical lymph nodes (LN) by flow cytometry. RESULTS: No differences among lung lobes were detected in any of the cell subpopulations tested. A low proportion of T cell subsets was detected in NB and 4YR groups in lung and BAL. Besides, the AW and 3M groups showed important changes in T cell subpopulations. CONCLUSIONS: These results suggest that in healthy animals the lung lobes behave as a homogeneous immune organ. T cells were detected in very low percentages at birth and in adult life, which may explain the high susceptibility to respiratory infections both early and later in life. Postweaning antigenic challenges and endocrine and sexual maturity at 3M had important effects on the development of the mucosal immune system. It was also evident that changes at mucosal sites were poorly correlated with PBMC and LN.
