Factors influencing fetal macrophage development: III. Immunocytochemical localization of cytokines and time-resolved expression of differentiation markers in organ-cultured rat lungs
✍ Scribed by Sorokin, Sergei P. ;Hoyt, Richard F. ;Reenstra, Wende R. ;McNelly, Nancy A.F.
- Book ID
- 102649783
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 558 KB
- Volume
- 248
- Category
- Article
- ISSN
- 0003-276X
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✦ Synopsis
Background:
Exogenous tnf alpha, il-1 beta, m-csf, and gm-csf all stimulate growth of macrophages arising in explanted fetal rat lungs. the present study examines the intrinsic availability of these factors in intact and organ-cultured lungs and utilizes expression of cytokines and marker proteins to explore the differentiation pathway followed by phagocytes in vitro.
Methods:
Factors and markers were localized immunocytochemically in paraffin sections of 14- and 15-day fetal rat lungs and lungs organ-cultured up to 7 days on serum-containing medium solidified with agar. western analyses for the cytokines were performed on lysates of whole 15-day lungs, and in situ hybridization of m-csf receptor mrna was carried out in sections of 14 + 2 day cultured lung.
Results:
Il-1 beta, m-csf, and gm-csf were demonstrated in the stroma of intact and cultured lungs by immunostaining, results confirmed by western blotting. tnf alpha appeared to be absent. a few precursors (angular cells) expressed the macrophage lineage marker rm-1 as early as day 14, and immunostaining became stronger and more widespread as the population matured and expanded in cultures. the ox-6 antibody to ia antigen first reacted with macrophages in 14 + 1 day explants, and within a week 50% of cells were positive. m-csf and mrna for its receptor were present at 14 + 2 days, as was pdgf, which had been demonstrated in the stroma and epithelium prior to explantation. definite reactivity for il-1 beta and gm-csf followed at 14 + 4 and 14 + 5 days.
Conclusions:
M-csf, gm-csf, and il-1 beta, but not tnf alpha, are available to replicating angular cells before and during their conversion to phagocytes. fetal lungs thus qualify as a hematopoietic tissue supportive of macrophages. the path of differentiation pursued in organ cultures involves early expression of structural elements (rm-1, ia antigen) followed by synthesis of cytokines of the tnf alpha cascade. immunostaining for both rm-1 and ox-6 suggests that fetal lung macrophages share a common heritage with antigen-presenting pulmonary dendritic cells.