title: A quantitative study on the activation of the alternative pathway of complement by mouldy hay dust and thermophilic actinomycetes.
abstract: Materials associated with the induction of farmer's lung were incubated with fresh normal human serum in the  presence of magnesium ethylene glycol tetra-acetic acid (MgEGTA) or ethylene diamine tetra-acetic acid (EDTA) and results compared with material known to activate the alternative pathway of complement--zymosan. Results show that Micropolyspora faeni organisms are as active as zymosan in reducing complement (C) levels in the presence of MgEGTA, with a 50% reduction in CH50 at approximately 140 mug/ml. Thermoactinomyces vulgaris organisms produced a 50% CH50 reduction at approximately 1-25 mg/ml and two samples of respirable mouldy hay dust (MHD) at approximately 5-6 mg/ml whereas extracts of M. faeni and T. vulgaris reduced the CH50 titre by 17% and 39% respectively at 16 mg/ml in the presence of MgEGTA. Organisms and extracts did not reduce the CH50 titre in the presence of EDTA even at the maximum concentration quoted by more than 3%, thus it is considered that alternative pathway activation was responsible for C utilization in the presence of MgEGTA. Respirable MHD used less than 4% available C at 4 mg/ml in the presence of EDTA but at 8 mg/ml dust 11% and 28% available CH50 were used compared with 79% and 81% respectively in the presence of MgEGTA. The elution of immunoglobulin binding material from MHD may be responsible for apparent CH50 consumption in the presence of EDTA.
mesh_terms: D000485:Allergens / Q000494:pharmacology; D000937:Antigen-Antibody Reactions; D002614:Chelating Agents / Q000494:pharmacology; D003165:Complement System Proteins / Q000378:metabolism*; D004391:Dust; D005203:Farmer's Lung / Q000276:immunology*; D006801:Humans; D066298:In Vitro Techniques; D008274:Magnesium / Q000494:pharmacology; D008848:Micromonosporaceae / Q000276:immunology*; D015054:Zymosan / Q000494:pharmacology
chemical_list: D000485:Allergens; D002614:Chelating Agents; D004391:Dust; D003165:Complement System Proteins; D015054:Zymosan; D008274:Magnesium