Veterinary immunology and immunopathology vol:104 issue:1-2 pages:21-31
date:Royal Vet & Agr Univ, Dept Clin Studies, DK-1870 Frederiksberg C, Copenhagen, Denmark; Inst Anim Sci & Hlth, ID Lelystad BV, Div Anim Sci, NL-8200 AB Lelystad, Netherlands; Univ Utrecht, Fac Vet Med, Dept Farm Anim Hlth, NL-3584 CL Utrecht, Netherlands; Univ Utrecht, Fac Vet Med, Dept Pathol, NL-3584 CL Utrecht, Netherlands
The aim of the present study was to characterise the serum amyloid A (SAA) response to intramammary inoculation of Escherichia coli and to examine the distribution of hepatically and extrahepatically produced SAA isoforms in plasma and milk from cows with mastitis. Milk and plasma SAA concentrations were determined before and after experimental induction of E. coli mastitis in six dairy cows. The milk SAA response was characterised by low or undetectable levels before inoculation, very rapid and large increases in concentration after inoculation, and rapid decline towards baseline levels after resolution of disease. In plasma from cows with experimentally induced E. coli mastitis, four hepatically derived SAA isoforms with apparent isoelectric point (pI) values of 5.8, 6.2, 6.8 and 7.4 were demonstrated by denaturing isoelectric focusing. In milk three highly alkaline isoforms with apparent pI values above 9.3 appeared 12 h post-inoculation. These isoforms were not present in any of the plasma samples, and it therefore seems likely that they were locally produced, tissue-specific isoforms. At 24-36 h post-inoculation one or more acidic isoforms corresponding to those found in plasma appeared in the milk samples. The isoforms demonstrated in plasma from cows with E. coli mastitis were also present in serum obtained from three cows with clinical Streptococcus uberis mastitis.