Recombinant Human IL-4 Protein

What it means: This IL-4 is produced in Human cells rather than in E. coli or insect cells. The manufacturer gives the source as human cells and does not name a specific cell line.

Why it matters:

• Expression in a human host lets the human IL-4 sequence be folded and processed by human cellular machinery.
• Production in human cells avoids bacterial host-cell contaminants that can affect sensitive immune-cell and stem-cell cultures.
• Together with the animal-free, xeno-free manufacturing format, it fits fully human culture systems.

How to interpret here: An expression system of Human cells means the IL-4 was made by a human cell line. It is intended for immune-regulation, allergy and inflammation research with human cells.

Tip: When switching from an IL-4 made in another host, re-titrate the working concentration rather than assuming the same activity per microgram.

What it means: The protein is Tag-free: no His, Fc, GST or other affinity tag is fused to the IL-4 sequence, and no tag needs to be removed before use.

Why it matters:

• A tag adds extra amino acids that can change folding, receptor binding, stability or the apparent molecular weight of a cytokine.
• In defined immune-cell and stem-cell culture media, every added component is a variable; a tag-free protein keeps the ligand close to the native sequence.
• Tag-free proteins are also preferred when results will be compared with published work that used untagged cytokines.

How to interpret here: Tag-free here means the vial contains only the IL-4 protein. It cannot be captured or detected with anti-His, anti-GST or Protein A reagents, so plan detection with an antibody against IL-4 itself.

What it means: Purity of >95% by SDS-PAGE means that when the protein is run on a denaturing gel and stained, at least 95% of the stained protein is the IL-4 band. It is the purity specification stated by the manufacturer.

Why it matters:

• High purity limits other proteins in the vial that could act on cells or interfere with downstream readouts.
• Dosing is done by protein mass, so a pure preparation makes the amount of cytokine added more accurate and comparable between experiments.
• Purity is stated together with endotoxin (<0.5 EU/µg), so both protein and non-protein contaminants are addressed.

How to interpret here: A specification of >95% by SDS-PAGE is a minimum value. The exact result for each lot is on the Certificate of Analysis (CoA), available from BioHippo on request.

Tip: SDS-PAGE purity shows how clean the preparation is, not how active it is; check the activity data separately.

What it means: The species is Human: the amino-acid sequence is that of human IL-4. The protein is also produced in human cells, so both the sequence and the expression host are human.

Why it matters:

• Matching the species of the cytokine to the species of the cells avoids differences in receptor binding between species.
• Human sequence is the usual choice for work with human primary immune cells, cell lines and stem-cell-derived cells.
• Recording the species in protocols matters because the same cytokine is sold from several species.

How to interpret here: Human here refers to the protein sequence. When reproducing a published protocol, check that it also used Human IL-4; if it used a protein from another species, the working concentration may need adjusting.

What it means: The protein is supplied Lyophilized, that is freeze-dried to a powder, from a 0.2 µm-filtered PBS solution and without carrier protein.

Why it matters:

• Lyophilized protein is more stable during storage than a solution, which gives a long shelf life when stored correctly.
• The stock concentration is chosen at reconstitution, so it can be matched to the volumes used in a protocol.
• As supplied, store at −20°C to −80°C for up to 12 months from receipt; after reconstitution keep it under sterile conditions at 2°C to 8°C for up to 1 month or at −20°C to −80°C for up to 3 months.

How to interpret here: Lyophilized means the vial must be reconstituted before use: briefly centrifuge the vial before opening, then reconstitute in sterile PBS containing 0.1% endotoxin-free recombinant human serum albumin.

Tip: Avoid repeated freeze–thaw cycles of the reconstituted protein; a manual-defrost freezer is recommended.

What it means: The molecular weight is 14–19 kDa, as stated by the manufacturer. The manufacturer describes IL-4 as a glycosylated monomer.

Why it matters:

• Molecular weight is the first check of identity when the protein is run on a gel or analysed by other methods.
• Glycosylation varies between molecules, so a glycosylated protein often runs as a broad band or several bands within the stated range.
• The manufacturer gives a nominal value; lot-level data are on the Certificate of Analysis.

How to interpret here: 14–19 kDa is a nominal value. Refer to the lot-specific Certificate of Analysis (CoA), available from BioHippo on request, for lot data.

Tip: Note whether a gel was run under reducing or non-reducing conditions when comparing band sizes.

What it means: Biological activity is tested by the ability of IL-4 to stimulate proliferation of human TF-1 cells, a human erythroleukemic indicator cell line. The assay value on this chip is TF-1 cell proliferation.

Why it matters:

• TF-1 is used as an indicator cell line, so a proliferation response to the protein shows that it engages its receptor.
• A cell-based activity test confirms that the protein is functionally active, which purity alone cannot show.
• The assay gives a common reference point when comparing lots or comparing this protein with other preparations tested the same way.

How to interpret here: TF-1 cell proliferation is the functional readout named by the manufacturer. No EC50 or ED50 value is given for this product, so the working dose should be confirmed in each experimental system.

Tip: Assay conditions are not a recommended working concentration; the dose should be optimized for each cell system and readout.