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An examination of the "star-phenomenon", a three component immunoprecipitation involving staphylococcal protein A
The co-precipitation called "star-phenomenon" occurred between the three component system: protein A, an IgG forming soluble complexes with protein A and F (ab')2-preparations of human IgG, guinea pig IgG or rabbit anti-staphylococcal IgG. Co-precipitation also occurred if the IgG was replaced by normal human Fc fragments. On a protein A column the human F (ab')2-preparation was separated into a major non-reactive and a minor reactive fraction. Only the latter contained Fc-structures, these being isolated on an anti-Fc column and found to belong to undigested IgG. The "star"-forming protein A reactive F (ab')2-fragments were washed through the anti-Fc column. The F (ab')2 fraction from rabbit anti-staphylococcal IgG contained no Fc-structures and only a small portion containing anti-protein A activity was active in co-precipitation.
The co-precipitation called "star-phenomenon" occurred between the three component system: protein A, an IgG forming soluble complexes with protein A and F (ab')2-preparations of human IgG, guinea pig IgG or rabbit anti-staphylococcal IgG. Co-precipitation also occurred if the IgG was replaced by normal human Fc fragments. On a protein A column the human F (ab')2-preparation was separated into a major non-reactive and a minor reactive fraction. Only the latter contained Fc-structures, these being isolated on an anti-Fc column and found to belong to undigested IgG. The "star"-forming protein A reactive F (ab')2-fragments were washed through the anti-Fc column. The F (ab')2 fraction from rabbit anti-staphylococcal IgG contained no Fc-structures and only a small portion containing anti-protein A activity was active in co-precipitation.