MMP9 and infection: Mmp8 (matrix metallopeptidase 8) transcript levels were significantly higher DBA/2J than C57Bl/6J at day 3 p.i. Prior to infection and shortly thereafter the Mmp9 (matrix metallopeptidase 9) expression levels were significantly up-regulated in C57Bl/6J compared to DBA/2J mice and the opposite was recorded at day 3 p.i.