DETERMINATION OF ANTIBODY TO PURIFIED MICROBIAL ANTIGENS BY AMMONIUM SULFATE COPRECIPITATION (FARR TECHNIQUE)
Abstract
The ammonium sulfate coprecipitation technique (ASCT) described by Farr in 1958 has been employed primarily with stable, well characterized antigens such as serum proteins. To facilitate study of the efficacy of immunization procedures and the role of serum antibody in resistance to infection, the application of ASCT to purified microbial antigens has been investigated. Studies with iodine 131-labeled protective antigen of Bacillus anthracis, using an equal volume of 2.8 M ammonium sulfate for coprecipitation, revealed differences in the combining capacities of various equine sera. Approximately 100% of a labeled protective antigen preparation was precipitated by 1:20 dilution of hyperimmune pony serum, whereas approximately 20% was precipitated by a 1:20 dilution of normal horse serum. Similarly, using 3.2 M ammonium sulfate for coprecipitation, radioiodine-labeled purified enterotoxin B of Staphylococcus aureus revealed differences in the combining capacities of various rabbit sera for the enterotoxin antigen. At a final concentration of 1 microgram per milliliter, essentially 100% of the labeled toxin was precipitated by a 1:10 dilution of a pooled anti-enterotoxin serum, whereas only 10 to 20% of the toxin was precipitated by normal rabbit sera. With both systems, over a considerable range of dilutions of normal and immune sera, the proportion of antigen precipitated by immune sera remained significantly greater. Thus, the ASCT yields sensitive and quantitative measurements of antibody reactive with these microbial antigens.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 1966
- Accession Number
- AD0476603
Entities
People
- George G. Wright
- Jack Gruber
Organizations
- United States Army Biological Warfare Laboratories