Anti-Cystatin-8 Rabbit Polyclonal Antibody

Frequently Asked Questions

What molecular weight band should I expect for Cystatin-8 on Western blot?

Cystatin-8 (CST8) migrates at approximately 14-16 kDa on reducing SDS-PAGE, consistent with its predicted molecular weight as a secreted cystatin family member. Note that reagent annotation ambiguity exists in some databases where the Q60676 entry refers to Ppp5c rather than authentic CST8. Verify your target sequence and antibody immunogen details before interpreting results. Expression is highest in epididymal tissue lysates. If working with recombinant protein, confirm the construct corresponds to the cystatin family member rather than the phosphatase.

Does this antibody cross-react with other cystatin family members?

Cross-reactivity with other cystatin superfamily members has not been systematically validated for this polyclonal reagent. Given the sequence homology within the cystatin family, particularly among type 2 cystatins, some degree of cross-reactivity is possible. If specificity is critical for your application, include lysates from tissues with differential cystatin expression patterns as negative controls, or use siRNA/CRISPR knockdown of CST8 to confirm band identity. The recommended 1:1000 dilution provides a reasonable starting point to minimize non-specific binding while maintaining signal.

Which human tissues express Cystatin-8 at detectable levels for Western blot?

Authentic CST8 expression is predominantly restricted to male reproductive tissues, with highest levels in the epididymis where it functions in sperm maturation. Expression in other human tissues is typically low or absent. For positive control lysates, prioritize epididymal tissue or testis samples. Many commercially available normal tissue panels may not include epididymis, so consider sourcing specialized reproductive tissue lysates. Seminal plasma may also contain secreted CST8. For negative controls, brain, liver, or lymphoid tissues are appropriate given the tissue-restricted expression pattern.

What starting dilution should I use for IHC with this Cystatin-8 antibody?

While this antibody is validated for Western blot at 1:1000, IHC applications typically require optimization starting around 1:100 to 1:500 for paraffin-embedded sections. Antigen retrieval is generally necessary for cystatins; citrate buffer (pH 6.0) heat-induced epitope retrieval is a reasonable first approach. Given CST8's secretory nature, expect cytoplasmic and extracellular staining patterns in epididymal epithelium. Testicular tissue sections serve as suitable positive controls. Run parallel sections with preimmune rabbit IgG at equivalent concentration to assess non-specific binding of this polyclonal reagent.

Can I use this antibody to detect mouse or rat Cystatin-8?

This antibody is validated only for human CST8. Cross-reactivity with mouse or rat orthologs is predicted but not experimentally confirmed. Sequence alignment between human and rodent cystatin-8 family members shows moderate conservation, suggesting potential cross-reactivity, but empirical testing with rodent tissue lysates is necessary. If working with mouse models, epididymal lysates provide the best test substrate. Be aware that rodent cystatin nomenclature differs somewhat from human, and the CRES subfamily designation is often used for related epididymal cystatins in mice.

What sample preparation considerations are important for detecting secreted Cystatin-8?

As a secreted cystatin, CST8 is present in both cellular lysates and extracellular fractions. For tissue homogenates, include protease inhibitors to prevent degradation by the cysteine proteases that CST8 naturally regulates. When analyzing conditioned media or biological fluids, concentration via ultrafiltration or precipitation may be necessary depending on secretion levels. The mature secreted form lacks the signal peptide, which affects the predicted molecular weight. For epididymal samples, luminal content may contain higher CST8 concentrations than epithelial cell lysates. Load equivalent protein amounts across samples for quantitative comparisons.

How should I store this polyclonal antibody to maintain long-term stability?

Store the antibody at -20°C as supplied. For frequent use, prepare working aliquots to avoid repeated freeze-thaw cycles, which can reduce polyclonal antibody titer and increase aggregation. Single freeze-thaw cycles are generally tolerated, but more than three cycles may compromise performance. Once diluted in blocking buffer for Western blot, the antibody can be stored at 4°C with 0.02% sodium azide for up to one week for re-probing, though fresh dilutions are preferable for quantitative work. Avoid storing diluted antibody for IHC applications; prepare fresh working solutions.

What controls should I include when characterizing Cystatin-8 expression in new samples?

Include both positive controls (epididymal or testicular lysate showing the expected 14-16 kDa band) and negative controls (tissues lacking CST8 expression, such as brain or liver) in each experiment. Given the annotation ambiguity noted with Q60676, consider validating target identity using a second independent antibody or mass spectrometry if this is your first characterization. For functional studies, recombinant CST8 protein serves as a sizing standard and epitope-blocking control. When quantifying expression changes, verify loading with total protein stain rather than relying solely on housekeeping proteins, particularly in reproductive tissues where dramatic remodeling occurs.