Purification of goat immunoglobulin G1 (IgG1) and IgG2 antibodies by use of Streptococcus dysgalactiae cells with Fc receptors.

The application of stabilised streptococcal cells for the purification of both immunoglobulin 1 (IgG1) and IgG2 subclasses from goat sera was evaluated. Guanidinium chloride extracted, lyophilised cells of the Lancefield Group C Streptococcus dysgalactiae Sc1 strain showed strong binding to goat IgG, reaching a capacity of approximately 1.4 mg IgG per 100 mg cells (dry weight). The IgG preparation obtained was of high quality. In immunoelectrophoretic analysis the preparation appeared to consist of pure IgG, whereas the high pressure liquid chromatography (HPLC) gel filtration and immunoblot analyses showed a very slight contamination (less than 1.3% of the total probe) with alpha 2-macroglobulin. The presence of both IgG subclasses in the preparation was verified by HPLC ion exchange chromatography. The adsorption procedure proved to be efficient and easy to perform without advanced technical equipment and the cells were reusable. As these streptococcal cells bind both IgG subclasses, this method presents an economical way for the small scale purification of goat IgG. Additionally the streptococcal cells may conveniently substitute Protein A bearing Staphylococcus aureus cells in various immunological assays.