Cytokine mRNA expression by lung biopsy tissue from asthmatic and normal subjects during culture

We have developed an ex vivo bronchial expiant model to study the importance of structural airway dements during antigen induced cytokine production by inflammatory cells in asthma. Lung biopsy tissue from 5 atopic mild asthmatics and 5 normal control subjects were cultured for 24h in serum-free media alone, supplemented with D. pteronyssimis allergen (Der p, 5,000 U/ml, ALK) or PHA (5 ug/mi). Reverse transcription potymerase chain reaction (RT-PCR) analysis was then performed on the tissue to detect cytokine mRNA transcripts. Biopsies from normal subjects pressed [L-6, IL-g and IFN-v in media alone, hi contrast, lung tissue from asthmatics cultured under identical conditions showed the additional expression of IL-5, IL-13, GM-CSF and TNFa. Stimulation of biopsies with Der p antigen did not change the cytokine mRNA profile of normal tissue but augmented the expression of IL-5 in the asthmatic lung. As expected, PHA challenge of the bronchial tissue in both groups induced the increased expression of most cytokines. To confirm the elevated IL-13 expression in the asthmatic tissue, we measured levels of this cytokine in the culture supernatant of all study subjects. The data showed an increased amount of IL-13 protein in the supernatants from asthmatic compared to normal biopsies. In conclusion, these results demonstrate that (a) bronchial tissue actively transcribes cytokine mRNA after 24h culture without any overt stimulation, (b) clear differences are evident in the spectrum of cytokines expressed by atopic asthmatic lung compared to normal tissue and (c) these effects are specific to the lung since the data differ from what was observed with peripheral blood mononuclear cells from the same individuals.