Abstract
Bovine milk is generally considered to be almost devoid of complement, on the basis of undetectable hemolytic activity, unless inflammation recruits plasma components. This study examines the deposition of complement components on a mastitis-causing isolate of Streptococcus agalactiae by enzyme-linked immunosorbent assay (ELISA). Neat milk from mid-lactating, uninflamed mammary glands (normal milk) effected marked C3 deposition on bacteria. Kinetic studies showed a protracted lag period (30 to 45 min) preceding C3 deposition, which required about 2 h to reach a maximum. Experiments with diluted serum suggested that this slow C3 deposition resulted mainly from the low concentration of certain components of complement in milk. Bacteria incubated in neat milk readily bound bovine conglutinin, indicating the presence of iC3b. Elution of covalently bound C3 fragments with hydroxylamine confirmed the deposition of C3b and iC3b on bacteria. Deposition of C4 on bacteria was not detected in neat milk, suggesting that C3 deposition did not result from the activation of the classical pathway. This was not the result of a lack of antibodies. However, C4 deposition could be obtained by adding purified bovine C1q to normal milk, and C3 deposition was accelerated, suggesting the participation of the classical pathway. The deposition of C1q on antibody-sensitized bacteria was impeded by milk compared with that of C1q diluted in phosphate-buffered saline. Concentrations of C1q in normal milk were very low, ranging from 150 to 250 ng/ml. Overall, these findings indicate that C1q was a limiting factor of the classical pathway in normal milk. The capacity of milk to deposit C3 fragments on mastitis-causing S. agalactiae prompts further studies to investigate its role in opsonophagocytosis.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.