Identification and isolation of two pentraxins from bovine serum

Two distinct pentraxin proteins were isolated from bovine serum by calcium-dependent affinity chromatography on high pyruvate agarose gel. One of the proteins cross-reacted specifically with certain rabbit anti-human CRP antisera and was therefore designated as bovine CRP. The other cross-reacted specifically with a sheep anti-human SAP antiserum and was therefore designated as bovine SAP. Although the mixture of these two pentraxins was not resolved by gel filtration chromatography, they were separated by solid phase absorption of the CRP with immobilized rabbit anti-human CRP antibodies. Their identity as pentraxins was confirmed by their electron microscopic appearance. Bovine CRP was composed of a single type of non-glycosylated subunit whilst bovine SAP contained two major types of glycosylated subunits and a minor polypeptide, the glycosylation of which was not determined. Serum concentrations were in the range of 5-40 mg/l and neither protein behaved as an acute phase reactant. No bovine serum protein undergoing calcium-dependent binding to phosphoryl choline or pneumococcal C-polysaccharide was obtained.