Recombinant Cytokines in Cell and Gene Therapy Manufacturing: Building More Consistent and Scalable Cell Culture Processes

Cell and gene therapies (CGTs) are advancing rapidly, creating new opportunities in cancer treatment, genetic disorders and regenerative medicine. As more therapies move from clinical development toward commercial manufacturing, the industry faces an important challenge: how to produce high-quality therapeutic cells with greater consistency, scalability and cost efficiency.

In November 2026, the U.S. FDA issued its final guidance on Potency Assurance for Cellular and Gene Therapy Products. The guidance highlights a comprehensive, risk-based approach to potency assurance, covering manufacturing process design, material control, in-process testing and lot-release assays. This reinforces the importance of controlling critical raw materials throughout the manufacturing lifecycle. FDA Guidance, November 2026.

Among these materials, recombinant cytokines and growth factors play a particularly important role. They regulate cell proliferation, survival, differentiation and functional activity, directly influencing the quality of the final cell product.

For developers working with T cells, NK cells and hematopoietic stem and progenitor cells (HSPCs), selecting reliable recombinant proteins is therefore an essential part of building robust cell culture processes.

Cytokines are signaling proteins that regulate communication between cells. In ex vivo cell therapy manufacturing, they are widely used to support cell activation, expansion, differentiation and phenotype maintenance.

Different cell types require distinct cytokine combinations and culture conditions.

T Cell Expansion and CAR-T Manufacturing

T cells are central to many adoptive cell therapies, including chimeric antigen receptor T-cell (CAR-T) therapy. During ex vivo expansion, cytokines help regulate proliferation, survival and differentiation.

Commonly used cytokines include:

IL-2: Supports T-cell activation and proliferation.

IL-7: Contributes to T-cell survival and homeostasis.

IL-15: Supports the maintenance and expansion of memory-like T-cell populations.

IL-21: Can be incorporated into selected protocols to influence T-cell differentiation and functional characteristics.

Importantly, cytokine selection is not simply about maximizing cell numbers. The balance between expansion, differentiation and functional characteristics must be considered when developing a manufacturing process.

A 2026 review in Nature Biomedical Engineering examined cytokine use across 292 clinical CAR-T reports and highlighted evolving approaches to cytokine selection, including interest in alternatives to conventional IL-2 exposure. The findings underline the need for more systematic evaluation of cytokine combinations and manufacturing parameters.

NK Cell Expansion

Natural killer (NK) cells are another important platform in cellular immunotherapy. Their expansion and functional maintenance depend on carefully controlled culture conditions.

Key cytokines include:

IL-2: Supports NK-cell proliferation and activation.

IL-15: Plays a central role in NK-cell development, survival and homeostasis.

IL-21: Used in selected expansion strategies to support NK-cell proliferation and functional characteristics.

The choice of cytokines, concentrations and feeding schedules should be optimized according to the cell source and intended application.

HSPC Expansion and Differentiation

Hematopoietic stem and progenitor cells are essential starting materials for hematopoietic stem cell transplantation and gene-modified cell therapies.

Their ex vivo expansion requires a coordinated combination of growth factors and cytokines, such as:

SCF (Stem Cell Factor): Supports HSPC survival and proliferation.

TPO (Thrombopoietin): Contributes to HSPC maintenance and megakaryocytic lineage development.

FLT3 Ligand: Supports the expansion and differentiation of hematopoietic progenitor populations.

IL-3: Promotes the proliferation and differentiation of hematopoietic progenitor cells.

IL-6: Participates in hematopoietic cell regulation and may be included in selected expansion systems.

Optimizing these factors is important for balancing cell expansion, phenotype retention and downstream functional performance.

As CGT manufacturing moves toward larger production scales, the quality and supply of raw materials become increasingly important.

Lot-to-Lot Consistency

Recombinant cytokines are biologically active materials. Differences in purity, biological activity, aggregation or impurity profiles may affect cell culture performance.

For manufacturers, consistent product specifications and activity verification help reduce variability between production batches and support process reproducibility.

Raw Material Quality and Safety

Cell therapy products are particularly sensitive to contamination risks because the final therapeutic product consists of living cells. Unlike many conventional biologics, these products cannot simply undergo terminal sterilization or conventional viral-clearance steps.

Consequently, raw material qualification and appropriate microbiological and viral safety controls are important considerations. Depending on the application and risk assessment, relevant quality attributes may include identity, purity, biological activity, endotoxin, sterility, mycoplasma and adventitious-agent testing.

Scalability and Supply Continuity

A cytokine that performs well in a small-scale research experiment may not automatically meet the requirements of larger manufacturing operations.

As processes scale up, manufacturers need dependable production capacity, stable specifications, technical documentation and supply continuity. These factors should be considered early in process development rather than addressed only when clinical manufacturing begins.

Choosing a recombinant protein supplier involves more than comparing price or purity specifications. Several factors should be evaluated together.

Biological activity: Functional assays, such as cell proliferation assays, help confirm that a protein performs as expected in a relevant biological system.

Purity and impurity profile: High purity and appropriate impurity controls help reduce unwanted effects in sensitive cell culture systems.

Endotoxin control: Low-endotoxin materials are particularly important for immune-cell applications, where endotoxin contamination may interfere with experimental outcomes and process evaluation.

Expression system and product design: CHO, HEK293 and E. coli expression platforms offer different production characteristics. The appropriate system depends on the protein's structure, intended application and quality requirements.

Documentation and traceability: Product specifications, Certificates of Analysis (CoAs), batch traceability and relevant quality documentation support material qualification and supplier assessment.

For clinical and commercial development, raw material requirements should be established according to the stage of development, intended use and applicable regulatory expectations. Research-use products should not be assumed to meet GMP requirements without appropriate qualification.

EastMabBio focuses on recombinant protein manufacturing, providing a portfolio of cytokines and growth factors for cell culture research and process development.

Our products support applications across stem cell research, immune cell culture and cell and gene therapy development.

Key product categories include:

HSPC expansion: SCF, TPO, FLT3 Ligand, IL-3 and IL-6.

T-cell culture: IL-2, IL-7, IL-15 and IL-21.

NK-cell expansion: IL-2, IL-15 and other relevant cytokines.

Stem cell and cell culture applications: A broad range of recombinant growth factors and supporting proteins.

With CHO, HEK293 and E. coli expression platforms, EastMabBio supports diverse recombinant protein production requirements. Our manufacturing capabilities include a 10,000 m² R&D and production base, a 4,000 m² GMP cleanroom facility and fermentation capacity of up to 1,000 L for prokaryotic and 500 L for eukaryotic production.

For customers developing advanced therapy manufacturing processes, EastMabBio also provides custom recombinant protein development and manufacturing support. Services can cover protein design, expression optimization, process development and scale-up, with GMP-focused manufacturing and quality documentation support according to project requirements.

The future of cell and gene therapy manufacturing will depend not only on advances in cell engineering, but also on the ability to establish reproducible, scalable and well-controlled manufacturing processes.

Recombinant cytokines are essential components of many cell expansion workflows. Their biological activity, batch consistency, quality controls and supply reliability can all contribute to process performance.

As the industry places greater emphasis on potency assurance and manufacturing consistency, selecting qualified raw materials and establishing reliable supplier partnerships will remain important priorities.

Looking for recombinant cytokines for your cell culture or CGT process development?

Explore EastMabBio's recombinant protein portfolio or contact our team to discuss customized protein solutions.

EastMabBio — High-quality recombinant protein manufacturer.

Website: https://www.eastmabbio.com

Email: product@eastmabbio.com