These are a family of apolipoproteins that are associated with high density lipoprotein when in serum.38 The mammary associated SAA3 isoform is also one of the first APP reported to increase during mastitis and previous proteomics studies have shown up-regulation of isoforms of SAA in milk in response to gram-negative and gram-positive pathogens.6,7,38 As for Hp, proteomic analysis identified the increase in SAA levels earlier than ELISA-based analysis4 demonstrating further that quantitative proteomics may be more sensitive than the forms of ELISA used previously. This evidence concerns the gene HP and mastitis.