Anti-MMP-12 Rabbit Polyclonal Antibody

Frequently Asked Questions

What is the expected molecular weight for MMP-12 on a Western blot?

MMP-12 migrates as a ~54 kDa band corresponding to the pro-enzyme form and a ~45 kDa band representing the active, processed enzyme after proteolytic removal of the pro-domain. In macrophage lysates or conditioned media, you may observe both forms depending on activation state. The mature catalytic domain is approximately 22 kDa, though this is less commonly detected with antibodies targeting the full-length sequence. Band intensity and relative proportions of pro- versus active forms vary with cell type, inflammatory stimuli, and sample preparation. Always include a positive control such as THP-1 or RAW 264.7 macrophage lysate.

What dilution should I start with for Western blot using this MMP-12 antibody?

The recommended starting dilution is 1:1000 for Western blot. This works well for lysates from macrophages or other MMP-12-expressing cells at typical loading amounts of 20-30 µg total protein per lane. If signal is weak, you can increase antibody concentration to 1:500 or enrich for secreted MMP-12 by concentrating conditioned media using centrifugal filters. Conversely, if background is high, titrate up to 1:2000. Blocking with 5% non-fat milk in TBST for one hour at room temperature generally provides clean results. The 100 µg pack size allows approximately 100 blots at 1:1000.

Is this MMP-12 antibody cross-reactive with mouse and rat samples?

The antibody is validated for human MMP-12 and predicted to cross-react with mouse, rat, non-human primate, and dog based on epitope sequence homology. Human and mouse MMP-12 share approximately 79% amino acid identity, with high conservation in the catalytic domain. We recommend empirical validation in your system, starting at 1:1000 dilution for Western blot. Mouse bone marrow-derived macrophages stimulated with LPS or IL-4 serve as useful positive controls. Rat alveolar macrophages also express MMP-12 under inflammatory conditions. If working with these species for the first time, include a human lysate as a reference standard.

Can I use this antibody for immunohistochemistry on lung tissue sections?

Yes, this antibody is validated for Western blot; IHC validation is in progress applications. For paraffin-embedded lung tissue, antigen retrieval is essential due to formalin crosslinking. Citrate buffer (pH 6.0) heat-mediated retrieval for 20 minutes typically works well for MMP-12. Macrophages in inflammatory infiltrates, particularly around areas of tissue remodeling or emphysematous regions, should show positive cytoplasmic and peri-cellular staining. Start with a 1:100 to 1:200 dilution and titrate as needed. Include known MMP-12-positive tissue such as atherosclerotic plaque or COPD lung as a positive control. Normal lung parenchyma generally shows minimal background.

What positive and negative controls should I use for MMP-12 experiments?

For positive controls, use lysates or conditioned media from phorbol ester-activated THP-1 macrophages, LPS-stimulated RAW 264.7 cells, or primary human monocyte-derived macrophages. MMP-12 expression is highly inducible and may be low in unstimulated cells. Recombinant human MMP-12 protein provides an additional molecular weight reference. Negative controls should include non-macrophage cell lines with negligible MMP-12 expression such as HEK293 or NIH-3T3 fibroblasts. For IHC, use serial sections incubated with rabbit IgG isotype control at matched concentration, and consider MMP-12 knockout tissue if available. Include a no-primary-antibody control to assess non-specific secondary binding.

Does MMP-12 require reducing conditions for Western blot detection?

Yes, reducing conditions are recommended for optimal MMP-12 detection. Prepare samples in SDS-PAGE loading buffer containing DTT or β-mercaptoethanol and heat at 95°C for five minutes. MMP-12 contains disulfide bonds in the catalytic domain and hemopexin-like domain that, if left intact, may alter migration or epitope accessibility. Under non-reducing conditions, you may observe higher molecular weight species due to inter- or intra-molecular disulfide bonding, complicating interpretation. Reducing conditions yield the expected 54 kDa and 45 kDa bands corresponding to pro-MMP-12 and active MMP-12. This is standard practice for most metalloproteinase Western blots.

How should I store this MMP-12 antibody and what is the shelf life?

Store the antibody at -20°C in small aliquots to avoid repeated freeze-thaw cycles, which can reduce titer and increase aggregation. The antibody is supplied as a polyclonal in a buffered solution, typically stable for at least 12 months under these conditions. For convenience, you can prepare working dilutions in blocking buffer containing 0.02% sodium azide and store at 4°C for up to one month for repeated Western blots. Avoid prolonged exposure to room temperature. If you observe increased background or decreased signal over time, prepare a fresh aliquot. The 100 µg size is sufficient for extensive experimentation when handled properly.

What is the biological role of MMP-12 and when is it expressed?

MMP-12, also called macrophage metalloelastase, is a zinc-dependent endopeptidase secreted primarily by activated macrophages during inflammation and tissue remodeling. It exhibits potent elastolytic activity, degrading elastin and other extracellular matrix proteins. Expression is highly upregulated in chronic obstructive pulmonary disease, atherosclerosis, and aneurysm formation where macrophage infiltration and matrix degradation are prominent. MMP-12 is also implicated in cancer metastasis and wound healing. Unlike constitutively expressed MMPs, MMP-12 is strongly inducible by inflammatory stimuli such as LPS, cytokines, or cigarette smoke extract. Expect low to absent expression in resting macrophages and require appropriate activation in your experimental model.