The long-range objective is to clarify the origin of """"""""resident"""""""" alveolar macrophages and the nature of factors regulating production of these unique lung cells that form the first line of defense against inhaled particles and microorganisms. It is known that in organ culture, embryonic mammalian lungs generate a replicating population of phagocytes indistinguishable from alveolar macrophages by morphological, functional, and immunocyto- chemical criteria. These cells are termed """"""""premedullary"""""""" because they appear prior to formation of the bone marrow and in the absence of circulating monocytes.
Specific aims of the proposed program are 1) to define the cell type or types that give rise to premedullary macrophages; 2) to clarify events occurring during transition from precursor to macrophage; 3) to determine the population kinetics and replicative capacity of alveolar macrophages having a premedullary origin; and 4) to identify local sources of factors which may trigger transformation of precursors and/or act to maintain the resulting differentiated phagocytes. Relative to aims 1 and 2, embryonic rat and hamster lungs will be fixed for transmission electron microscopy at short intervals during the first 24 hr. in organ culture. Thin sections will be surveyed for number and types of potential leukocyte precursors and for transitional forms between precursor and mature phagocyte. Nascent macrophages will be traced back as closely as possible to their origin b"""""""" enzyme cytochemistry (acid phosphatase, NADPH oxidase) and immunocytochemical localizations of leukocyte and macrophage-specific marker proteins. Relative to aim 3, organ cultured lungs will be grown on medium containing 3H-thymidine and processed for light microscopic autoradiography. Cell cycle times and replication rates will be determined after continuous labeling by use of standard statistical methods. Respecting aim 4, organ cultured lungs and lung explants will be examined immunocytochemically to localize factors known to influence macrophage differentiation and proliferation in other systems. These include hematopoietic colony-stimulating factors (CSFs), platelet-derived growth factor, and hemopoietin-l. Efforts will also be made to influence macrophage production and growth within explanted lungs and on adjacent culture medium by direct application of CSFs. Results of these studies will be evaluated by transmission electron microscopy and by 3H-thymidine labeling and light microscopic autoradiography of Giemsa-stained 2 mu m glycol methacrylate sections.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL033070-07
Application #
3344661
Study Section
Pathology A Study Section (PTHA)
Project Start
1984-07-01
Project End
1992-06-30
Budget Start
1990-07-01
Budget End
1991-06-30
Support Year
7
Fiscal Year
1990
Total Cost
Indirect Cost
Name
Boston University
Department
Type
Schools of Medicine
DUNS #
604483045
City
Boston
State
MA
Country
United States
Zip Code
02118
Sorokin, S P; Hoyt Jr, R F; Reenstra, W R et al. (1997) Factors influencing fetal macrophage development: III. Immunocytochemical localization of cytokines and time-resolved expression of differentiation markers in organ-cultured rat lungs. Anat Rec 248:93-103
Sorokin, S P; McNelly, N A; Hoyt Jr, R F (1996) Factors influencing fetal macrophage development: II. Effects of the PDGF subfamily of protein-tyrosine kinase receptor ligands as studied in organ-cultured rat lungs. Anat Rec 246:498-506
Sorokin, S P; Hoyt Jr, R F; McNelly, N A (1996) Factors influencing fetal macrophage development: I. Reactions of the tumor necrosis factor-alpha cascade and their inhibitors. Anat Rec 246:481-97
Sorokin, S P; McNelly, N A; Hoyt Jr, R F (1994) Exogenous cytokines enhance survival of macrophages from organ cultured embryonic rat tissues. Anat Rec 240:398-406
Sorokin, S P; McNelly, N A; Hoyt Jr, R F et al. (1994) Precursors of macrophages in embryonic rat lungs fail to exhibit granulocyte-forming potential. Anat Rec 240:387-97
Sorokin, S P; McNelly, N A; Hoyt Jr, R F (1994) Early development of macrophages in intact and organ cultured hearts of rat embryos. Anat Rec 239:306-14
Sorokin, S P; Hoyt Jr, R F (1992) Macrophage development: I. Rationale for using Griffonia simplicifolia isolectin B4 as a marker for the line. Anat Rec 232:520-6
Sorokin, S P; McNelly, N A; Hoyt Jr, R F (1992) CFU-rAM, the origin of lung macrophages, and the macrophage lineage. Am J Physiol 263:L299-307
Sorokin, S P; Hoyt Jr, R F; Blunt, D G et al. (1992) Macrophage development: II. Early ontogeny of macrophage populations in brain, liver, and lungs of rat embryos as revealed by a lectin marker. Anat Rec 232:527-50
Sorokin, S P; McNelly, N A; Blunt, D G et al. (1992) Macrophage development: III. Transformation of pulmonary macrophages from precursors in fetal lungs and their later maturation in organ culture. Anat Rec 232:551-71

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