Fig. 1
Experimental design and functional validation of the human lung tissue explants (HLTE) model. A Outline of the experimental procedure. After removal from the explanted lung, tissue was divided into pieces of approx. 30 mg and then incubated in medium overnight. HLTE pieces were infected with 2.0 × 105 FFU/ml of influenza virus strain A/Giessen /6/2009 H1N1 (in short IAV), 5 × 106 CFU/ml M. bovis strain H37Rv (BCG), or 1 × 108/ml P. aeruginosa strain PA14. All analyses were performed 24 h post infection (p.i.) unless indicated otherwise. B Comparison of two methods of tissue preservation before RNA extraction. HLTE pieces were either snap frozen in liquid nitrogen (n = 20) or incubated in RNAlater at 4 °C overnight (n = 38) before storage at − 80 °C, followed by RNA extraction. Y-axis = RNA integrity number (RIN). C Time course of LDH release from uninfected or IAV-infected HLTE pieces (n = 3 per group). LDH was measured in tissue culture supernatants and is expressed as % of LDH extracted from lysed tissue control. D Time course of IAV hemagglutinin (HA) mRNA levels (RT-qPCR), indicating transcription of viral RNA (n = 6). E Differences in cytokine/chemokine induction by infection with IAV, BCG, and P. aeruginosa. Upper row: protein concentrations measured by EIA. Bottom row: mRNA levels measured by RT-qPCR relative to mock-infected HLTE, using GAPDH as internal reference. n = 9. *p ≤ 0.05; **p ≤ 0.01; ***p ≤ 0.001; ****p ≤ 0.0001; B–D = unpaired parametric T test; E = Mann–Whitney U test. Data represent means ± SEM