Classification and Selection Criteria for Cytokine Products
The year 2017 marked the breakthrough for CAR-T cell therapy, sparking significant interest in the field of cell therapy, including stem cell therapy, TCR-T therapy, and more. Nearly all cell therapies share a common aspect: the need for cytokines to induce cell proliferation or differentiation.
Although cytokines are present in very small quantities in cells, they are highly diverse and play broad roles. But what exactly are cytokines? What functions do they serve? How do you select the appropriate cytokines? Let’s explore these questions.
What Are Cytokines?
To maintain physiological balance, resist pathogen invasion, and prevent tumor development, many cells—particularly immune cells—synthesize and secrete small, soluble proteins and peptides. This group of factors includes hundreds of known molecules, collectively called cytokines.
Cytokines facilitate communication between cells and regulate immune responses, cell growth and differentiation, and hematopoiesis. They are also involved in inflammatory and pathological processes, and in abnormal situations, they may cause symptoms like fever, inflammation, or shock.
Cytokines include lymphokines (produced by lymphocytes), monokines (produced by monocytes), various growth factors, etc.
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Classification of Cytokines:
■?Interleukins (IL):?Produced by lymphocytes, monocytes, or other cells, interleukins play a key role in cell-to-cell interactions, immune regulation, hematopoiesis, and inflammation.
■ Colony-Stimulating Factors (CSF):?These stimulate the proliferation and differentiation of hematopoietic stem cells and progenitor cells at various stages of development and enhance the functionality of mature cells.
■ Interferons (IFN):?Initially discovered in virus-infected cells, interferons inhibit the replication of other viruses. Produced by leukocytes, fibroblasts, and activated T cells, they exhibit antiviral, antitumor, and immunoregulatory effects.
■ Tumor Necrosis Factors (TNF): Named for their ability to induce tumor cell death, TNFs also regulate immune responses and play a role in fever and inflammation.
■ Transforming Growth Factor-β Family (TGF-β):?Produced by various cells, this family includes TGF-β1, TGF-β2, TGF-β3, BMPs (Bone Morphogenetic Proteins),?etc.
■ Chemokines: These direct cell migration, particularly in drawing leukocytes to infection sites, and are essential in inflammatory responses.
■?Other Cytokines:?These include Epidermal Growth Factor (EGF), Platelet-Derived Growth Factor (PDGF), Fibroblast Growth Factor (FGF), Hepatocyte Growth Factor (HGF), Leukemia Inhibitory Factor (LIF), Nerve Growth Factor (NGF), and others.
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Functions of Cytokines:
Cytokine research is vital for understanding immune regulation at the molecular level and has significant implications for disease prevention, diagnosis, and treatment.
The use of recombinant cytokines produced via genetic engineering has already demonstrated therapeutic efficacy in treating tumors, infections, inflammation, and hematopoietic disorders.
Cytokine actions can be categorized as:
l Immune response and regulation
l Hematopoiesis stimulation
l Interaction with the neuro-endocrine-immune system
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Types of cytokine signaling:
l Autocrine – Affecting the same cell that secretes them.
l Paracrine – Affecting nearby cells.
l Endocrine – Affecting distant cells through circulation.
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Key characteristics?include pleiotropy, redundancy, synergy, and antagonism.
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Important Considerations: Cytokine Selection Criteria
Species Origin:
We offer cytokines derived from various species, such as human, mouse, and rat. The choice of species depends on experimental needs.
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Typically, cytokines with over 80% homology between species can exhibit cross-reactivity, and such products are recommended for use.
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Expression System:
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The most common systems for expressing cytokines are E. coli?and mammalian cells, although yeast and insect systems are also used. Most clinical and laboratory cytokines are derived from E. coli.?
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It is important to understand the purpose of your research before selecting an expression system, as some proteins require post-translational modifications for activity, which bacterial cells cannot provide but mammalian cells can. Always review the product documentation for details on the protein's origin.
Common Recombinant Protein Expression Systems
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Quality Control:
The quality of cytokines can significantly impact experimental outcomes. Poor-quality products may cause failed experiments, leading to wasted time and resources. Reputable brands conduct extensive quality control on their proteins to ensure their reliability. For example, if you’re using cytokines as animal immunogens to study antibodies, a purity level of over 80% is adequate. For crystallization studies, purity should exceed 95%.