Receptor-mediated binding of C1 q on pulmonary endothelial cells

Conference · Sat Mar 01 04:00:00 EST 1986 · Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States)

OSTI ID:5453610

Zhang, S C; Schultz, D; Ryan, U

Normal undamaged pulmonary endothelial cells (EC) do not express receptors for C3b or the Fc portion of IgG, but both receptors become unmasked after viral infection or exposure to white cell lysates. Here, highly purified human C1q was labeled with /sup 125/I, and the globular subunits were separated from the collagenous portion by collagenase digestion and chromatography. Bovine pulmonary artery EC were cultured without exposure to proteolytic enzymes. Binding assays were carried out at 0/sup 0/C, pH 7.4, ..mu.. = 0.15. Results showed that /sup 125/I-C1q binds to EC, the binding is dose-dependent, and the receptor is saturable. Saturation was approached at a C1q concentration of ca 0.1 ug. By Scatchard analysis, maximum binding was 0.219 pmoles in a volume of 250 ..mu..l for 7 x 10/sup 5/ cells, and the average number of binding sites per cell was 1.88 x 10/sup 5/. Isolated /sup 125/I-C1q heads do not bind, and when native /sup 125/I-C1q was bound to EC radioactivity was eliminated after collagenase treatment for 4 h at 37/sup 0/C. Thus, C1q binds to EC via the collagenous portion. That Fc receptors (globular heads) are exposed was shown by rosette formation with EA and EC bound C1q. Using similar conditions, native C1(C1w x 2C1r x 2C1s) did not bind to EC. These results suggest a mechanism for localizing immune complexes on undamaged pulmonary vessels which may be important for initiation of the inflammatory response.

• Research Organization: Univ. of Miami Medical School, FL
• OSTI ID: 5453610
• Report Number(s): CONF-8604222-
• Conference Information: Journal Name: Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States) Journal Volume: 45:3
• Country of Publication: United States
• Language: English

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550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ANIMAL TISSUES
BETA DECAY RADIOISOTOPES
BIOCHEMICAL REACTION KINETICS
BODY
COMPLEMENT
DAYS LIVING RADIOISOTOPES
DOSE-RESPONSE RELATIONSHIPS
ELECTRON CAPTURE RADIOISOTOPES
ENDOTHELIUM
ENZYMES
HYDROLASES
INFLAMMATION
INTERMEDIATE MASS NUCLEI
IODINE 125
IODINE ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
LUNGS
MEMBRANE PROTEINS
NUCLEI
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
ORGANS
PATHOLOGICAL CHANGES
PEPTIDE HYDROLASES
PROTEINS
RADIOISOTOPES
REACTION KINETICS
RECEPTORS
RESPIRATORY SYSTEM
SYMPTOMS
TISSUES
TRACER TECHNIQUES