(D, top) MT1-MMP protein content was estimated by Western blot analysis of total cellular extracts from fresh monocytes or monocytes attached to plates coated as described for panel A. LPS stimulation for 16 hours was included as a positive control. Anti-MT1-MMP LEM-2/15 mAb recognizes immature and mature forms of MT1-MMP of 63 kDa and 60 kDa, respectively. (D, bottom) The arithmetic means and SD of the fold induction of the ratio of MT1-MMP to β-actin levels estimated by densitometry are represented (an arbitrary value of 1 was assigned to the MT1-MMP/β-actin ratio in freshly isolated monocytes). n = 3. ^*P < .05.