Lung epithelial H292 cells induce differentiation of immature human HMC-1 mast cells by interleukin-6 and stem cell factor.
BACKGROUND
Immature mast cells migrate into tissues where they differentiate into mature mast cells under the influence of local factors. In the airways of asthmatics increased numbers of chronically activated mast cells are located nearby the airway epithelium.


OBJECTIVE
The aim of this study was to evaluate whether and, if so, which products released by epithelial cells may affect mast cell proliferation and differentiation.


METHODS
We performed in vitro studies using the human lung mucoepidermoid carcinoma-derived H292 cell line and the immature human mast cell line, HMC-1. Proliferation was assessed by 3H-thymidine incorporation. Differentiation of HMC-1 cells was inferred from tryptase production.


RESULTS
Exposure of HMC-1 cells to medium conditioned for 48 h by H292 cells resulted in a reduction of proliferation with 65 +/- 4.9% (mean +/- SEM, n = 9) at day 5. Culturing HMC-1 cells for 8 days in the presence of H292-conditioned medium resulted in morphological changes indicative of differentiation, and in a 3.0 +/- 0.4-fold increase of tryptase production (P = 0.0039, n = 9). Conditioned medium from H292 cells that were stimulated by LPS also inhibited HMC-1 proliferation. Inhibitory antibodies against two mediators from H292 cells, interleukin-6 (IL-6) and stem cell factor (SCF), abolished the increase in HMC-1 tryptase production induced by H292-conditioned medium. Recombinant human (rh) IL-6, but not rhSCF, reduced HMC-1 proliferation with 44% and 13% at day 3 and 5, respectively. Surprisingly, rhIL-6 did not increase HMC-1 tryptase production significantly whereas incubation with rhSCF did (1.5 +/- 0.1-fold, P = 0.002, n = 10) although the increase was less than observed for conditioned medium.


CONCLUSIONS
Epithelial-derived IL-6 and SCF are implicated in differentiation of HMC-1 cells but additional factors are not excluded. As activated primary bronchial epithelial cells also express IL-6 and SCF, it should be considered that these cells are involved in mast cell differentiation within the airways, particularly in diseases where epithelial cells are activated, such as asthma.
Pompen
M
M
Department of Pulmonology; Clinical and Laboratory Immunology Unit, Amsterdam, The Netherlands.
Smids
B S
BS
Dingemans
K P
KP
Jansen
H M
HM
Out
T A
TA
Lutter
R
R
D000906:Antibodies / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D053818:Chymases; D017077:Culture Media, Conditioned; D003594:Cytoplasmic Granules / Q000187:drug effects / Q000378:metabolism; D004847:Epithelial Cells / Q000502:physiology*; D006412:Hematopoietic Stem Cells / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D015850:Interleukin-6 / Q000235:genetics / Q000276:immunology / Q000494:pharmacology / Q000502:physiology*; D008168:Lung / Q000166:cytology / Q000502:physiology*; D008407:Mast Cells / Q000187:drug effects / Q000201:enzymology / Q000502:physiology*; D011994:Recombinant Proteins / Q000494:pharmacology; D012697:Serine Endopeptidases / Q000378:metabolism; D019089:Stem Cell Factor / Q000235:genetics / Q000276:immunology / Q000494:pharmacology / Q000502:physiology*; D013997:Time Factors; D053802:Tryptases; D014407:Tumor Cells, Cultured
D000906:Antibodies; D017077:Culture Media, Conditioned; D015850:Interleukin-6; D011994:Recombinant Proteins; D019089:Stem Cell Factor; D012697:Serine Endopeptidases; C083294:chymase 2; D053818:Chymases; D053802:Tryptases