MMP9 and infection: In the case of macrophages, the LPS of A. Actinomycetemcomitans induces the expression of MMP-9 as described previously [68]; likewise, in our hands, using the complete bacteria, we found a higher expression of this molecule but without a differential expression pattern by a specific serotype, except at 2 h on the part of serotype b compared with serotypes a and c, but reaching similar levels for all serotypes at 24 h post-infection.