Anti-MMP-18 Rabbit Polyclonal Antibody

Frequently Asked Questions

What molecular weight band should I expect for MMP-18 on a Western blot?

MMP-18 is synthesized as an inactive zymogen with a predicted molecular weight of approximately 53–55 kDa for the full-length proenzyme. Upon activation by propeptide cleavage, the mature catalytic domain runs at roughly 42–45 kDa. In cell lysates you may observe both forms depending on activation status. Xenopus MMP-18 shares functional homology with mammalian MMP-1, which behaves similarly. If you see only the pro-form, consider whether your sample contains active extracellular proteinases or whether cells have been stimulated to secrete and activate the enzyme.

Is this MMP-18 antibody validated for human samples or only Xenopus?

This rabbit polyclonal is validated for human samples by Western blot. Although MMP-18 was originally identified in Xenopus, the epitope sequence shares substantial homology with human MMP-1 and related collagenases, enabling cross-reactivity. We also list pig as a potential reactive species, though validation data are limited. If you are working with non-human primate or rodent samples, expect weaker or no signal because rodents lack a direct MMP-18 ortholog and rely on MMP-13 and other collagenases for similar ECM remodeling functions.

What dilution should I start with for Western blot of MMP-18?

We recommend starting at 1:1000 for Western blot, which has been validated with this antibody. Depending on expression level and sample preparation, you may titrate between 1:500 and 1:2000. MMP-18 is a secreted proteinase, so conditioned media and ECM-enriched fractions typically yield stronger signal than whole-cell lysates. If signal is weak, confirm that your samples contain activated or secreted MMP rather than intracellular pro-form only, and consider concentrating conditioned medium by ultrafiltration or acetone precipitation before loading.

Can I use this antibody for immunohistochemistry on tissue sections?

Yes, Triple Point Biologics antibodies are validated for immunohistochemistry as a brand-wide capability, and this MMP-18 antibody is suitable for IHC. Because MMPs are secreted into the extracellular matrix, you should expect staining in stromal compartments, around remodeling connective tissue, and at sites of collagen turnover rather than strong intracellular signal. Antigen retrieval is typically required; citrate buffer at pH 6.0 is a reasonable starting point for collagenase epitopes. Titrate dilution from 1:100 to 1:500 depending on your detection system and tissue fixation protocol.

Does MMP-18 have splice isoforms that will show multiple bands?

MMP-18 does not have well-characterized splice isoforms that produce distinct protein products. The most common heterogeneity you will observe arises from post-translational processing: the inactive pro-form versus the cleaved active enzyme, and potential glycosylation differences depending on cell type. Additional lower-molecular-weight bands may reflect autocatalytic degradation or cleavage by other matrix metalloproteinases in your sample. If you see a complex banding pattern, consider including protease inhibitors during lysis and treating parallel samples with EDTA or a metalloproteinase inhibitor to distinguish zymogen from processed forms.

What positive control sample should I use to validate MMP-18 antibody staining?

Fibroblasts or mesenchymal cells stimulated with IL-1β or TNF-α for 24–48 hours are a reliable positive control because these cytokines upregulate collagenase expression and secretion into conditioned medium. Alternatively, tissue undergoing active remodeling—such as healing wounds, tumor stroma, or inflamed connective tissue—will express MMP-18 and related collagenases. For Western blot, load both cell lysate and concentrated conditioned medium side-by-side; the secreted fraction should yield a clearer signal. Recombinant MMP-1 or MMP-18 protein can serve as a sizing standard if cross-reactivity is confirmed.

How should I store this MMP-18 antibody and how long will it remain stable?

Store the antibody at –20°C as supplied. For routine use, prepare small aliquots to avoid repeated freeze-thaw cycles, which can reduce titre and increase background. An aliquot kept at 4°C with 0.02 percent sodium azide as preservative is stable for several weeks and convenient for daily experiments. Triple Point Biologics has manufactured proteinase antibodies since 1994, and our polyclonals typically retain specificity for at least two years under proper storage. If you observe declining signal or increased non-specific bands over time, thaw a fresh aliquot rather than increasing concentration.

Will this antibody cross-react with other MMPs like MMP-1 or MMP-13?

Cross-reactivity with MMP-1 is possible because MMP-18 shares substantial functional and sequence homology with mammalian MMP-1; both are interstitial collagenases that cleave fibrillar collagens. This may actually be advantageous if you are studying collagenase activity broadly in human samples, where MMP-1 is the dominant ortholog. Cross-reactivity with MMP-13 is less likely but not excluded. If isoform specificity is critical for your experiment, run parallel blots with lysates overexpressing individual MMPs or knock down your target with siRNA to confirm the band identity. We report validated human reactivity; specificity claims require your own epitope mapping.