Name: ProSpec Bio Human Platelet Factor-4 (CXCL4)
Brand: ProSpec Bio
SKU: PSB-CHM-234
Availability: InStock

<h2 data-section-id="6k2g2o" data-start="0" data-end="37">What are cytokines and chemokines?</h2>
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Cytokines are small signaling proteins, typically 5&ndash;25 kDa, secreted by a broad range of cell types &mdash; immune cells (macrophages, T and B lymphocytes, mast cells) and non-immune cells (endothelial cells, fibroblasts, stromal cells) &mdash; that act as intercellular messengers regulating processes from inflammation and immune activation to cell proliferation, differentiation, and apoptosis. Chemokines are a structurally defined subset of cytokines: approximately 47 small proteins (8&ndash;10 kDa) sharing four conserved cysteine residues that determine their three-dimensional structure, with the primary function of directing cell migration (chemotaxis). Together with interleukins, interferons, and the TNF superfamily, cytokines and chemokines form the molecular vocabulary of intercellular immune communication &mdash; and are increasingly used as defined research reagents in immune cell culture, stem cell differentiation, and cell therapy manufacturing.
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<h2 dir="ltr">What you'll find in this category: </h2>
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Chemotactic Gradients: Purified proteins engineered to direct cell movement and study trafficking pathways.
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Pro-Inflammatory Signalers: Stable molecular assets designed to trigger predictable cellular defense cascades.
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Regulatory Cytokines: Finely tuned signaling factors built to control cell survival and activation networks.
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<h2 data-section-id="1psyrv9" data-start="1363" data-end="1404">How to choose cytokines and chemokines</h2>
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Functional class: interleukins, interferons, TNF superfamily, chemokines
Interleukins &mdash; more than 40 identified &mdash; have distinct and overlapping functions across inter-leukocyte and broader intercellular communication, making interleukin selection highly application-specific (e.g., IL-2 for T-cell expansion, IL-6 for inflammatory signaling studies). Interferons (Type I: IFN-&alpha;/-&beta;/-&tau;/-&omega;; Type II: IFN-&gamma;; Type III) provide antiviral and immune-regulatory signaling, each type activating distinct pathways. The TNF superfamily comprises 19 proteins with both pro-inflammatory and anti-inflammatory members regulating innate/adaptive immune cell activity, inflammation, and apoptosis. Chemokines direct chemotaxis via canonical GPCR receptors (stimulating migration) and atypical scavenger receptors (regulating chemokine availability).
Structural classification and receptor families
Beyond functional class, cytokines are grouped by structural similarity and receptor specificity: four-helix bundle cytokines (with IL-2 subfamily as one branch, signaling through class I/II cytokine receptors), beta-trefoil cytokines, cysteine-knot cytokines, chemokines, and TNF superfamily cytokines. This structural classification is practically useful for predicting receptor cross-reactivity and signaling pathway overlap when designing multi-cytokine experiments.
Grade selection: RUO to GMP/animal-free
RUO cytokines and chemokines are standard for academic and industry research. Animal-free proteins &mdash; produced using the same expression systems and manufacturing methods as GMP-grade equivalents &mdash; provide a defined-conditions transition pathway from preclinical research toward clinical manufacturing, eliminating regulatory and ethical concerns associated with animal-derived components. GMP-grade cytokines are manufactured under guidelines permitting use as ancillary materials in cell therapy manufacturing, with extensive QC testing and full source/manufacturing traceability documentation &mdash; consistent with the RUO/preclinical/GMP framework described for Recombinant Proteins generally.
Application context: immune and stem cell culture
Cytokines for immune cell culture (T-cell expansion using IL-2/IL-7/IL-15/IL-21) and stem cell culture (cytokines influencing differentiation and proliferation) represent two major application contexts within this category, each with cytokine selections specific to the target cell behavior.
Disease research and therapeutic targeting
Cytokines and chemokines are implicated across allergy, autoimmunity, and tumor development/progression, and are frequently studied as therapeutic targets due to their protein nature, small molecular weight, and minute blood concentrations enabling both analytical study and targeted intervention. Examples span IL-6/TNF-&alpha; as targets in neuroinflammatory and autoimmune neurology (with anti-IL-6 and anti-TNF-&alpha; therapies in clinical use) and chemokine receptor (e.g., CXCR3 isoform) characterization relevant to 3D cell migration device research.
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<h2 data-section-id="1fljvas" data-start="5144" data-end="5169">Specifications context</h2>
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The structural classification of cytokines into four-helix bundle, beta-trefoil, cysteine-knot, chemokine, and TNF superfamily groups reflects receptor complex composition and signaling specificity documented across the cytokine/receptor research literature. More than 40 interleukins and 19 TNF superfamily proteins are presently identified, with chemokines comprising approximately 47 small proteins defined by conserved cysteine residue positioning. As of 2026, animal-free GMP-equivalent cytokine manufacturing is an increasing share of new product introductions, supporting the preclinical-to-clinical transition pathway for cell therapy applications.
For broader growth factor and hormone context, see Growth Factors &amp; Hormones. For platelet-derived growth factor sources, see Blood Products &amp; Biofluids.
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Cytokines & Chemokines

ProSpec Bio

Key Specifications

ProSpec Bio Human Platelet Factor-4 (CXCL4)

Human Platelet Factor-4 (CXCL4) by ProSpec Bio is human platelet factor 4 (PF4, CXCL4) purified from human platelets, a 70-amino-acid protein of 7.8 kDa that is more than 95% pure. It is supplied lyophilized in 5 µg, 20 µg and 1 mg sizes for platelet and angiogenesis research. Purity is determined by SDS-PAGE and RP-HPLC.