Recombinant Human Interleukin-22 protein (IL22) (Active)

What is IL-22 and what are its primary biological functions?

IL-22 is a member of the IL-10 family of cytokines comprising 146 amino acids (positions 34 to 179 in the full-length protein) with a molecular weight of approximately 17 kDa. Unlike most cytokines, IL-22 primarily targets non-immune cells, particularly epithelial cells in barrier tissues rather than immune cells . It plays a critical role in modulating tissue responses during inflammation and is essential for the regeneration of epithelial cells to maintain barrier function after injury and prevent further tissue damage . IL-22 promotes cell survival and proliferation through activation of multiple signaling pathways, including STAT3, ERK1/2, and PI3K/AKT pathways .

Which receptor complex does IL-22 signal through?

IL-22 signals through a heterodimeric receptor complex composed of two subunits: the specific receptor IL-22RA1 (present on non-immune cells in various organs) and the shared subunit IL-10RB . The binding of IL-22 to IL-22RA1 induces the activation of tyrosine kinases JAK1 and TYK2, which subsequently activate STAT3 . This receptor specificity explains why IL-22 primarily acts on epithelial cells rather than immune cells, as IL-22RA1 expression is restricted to non-immune cells in various organs .

What are the primary cellular sources of IL-22?

Multiple immune cell populations produce IL-22, including:

• CD4+ T-helper cells

• γδ T-cells

• Natural killer T (NKT) cells

• Group 3 innate lymphoid cells (ILC3s)

Studies using reporter mice have shown that following exposure to inflammatory stimuli (such as cigarette smoke), CD4+ T-cells, NKT-cells, and ILC3s are the major IL-22-producing cells, while NKT-cells are the dominant source of dual IL-17A+IL-22+ cells .

What are the critical considerations for using recombinant IL-22 in experimental systems?

When working with recombinant human IL-22 protein:

• Purity assessment: Verify protein purity (≥95% is typically suitable for research applications) and endotoxin levels (should be ≤0.005 EU/μg) to avoid experimental artifacts .

• Biological activity verification: Confirm the biological activity of the recombinant protein through functional assays, such as STAT3 phosphorylation in responsive cell lines.

• Storage and handling: Store lyophilized protein at -20°C and reconstituted protein in small aliquots at -80°C to prevent freeze-thaw cycles. Always use low-binding tubes and avoid repeated freeze-thaw cycles.

• Dose determination: Appropriate concentrations typically range from 10-100 ng/mL for in vitro studies, but dose-response experiments should be conducted for each experimental system.

• Expression system compatibility: Consider that recombinant IL-22 expressed in HEK293 cells (as mentioned in search result ) may have post-translational modifications more similar to native human IL-22 than bacteria-derived proteins.

What methods can be used to study IL-22 signaling mechanisms?

To investigate IL-22 signaling mechanisms:

• Phospho-specific western blotting: To detect activation of STAT3, ERK1/2, and PI3K/AKT pathways following IL-22 stimulation .

• Transcriptional reporter assays: Using STAT3-responsive elements to quantify IL-22-induced transcriptional activation.

• Immunoprecipitation: To study complex formation between IL-22RA1, IL-10RB, and downstream signaling molecules like JAK1 and TYK2.

• RNA sequencing: For unbiased identification of IL-22-regulated genes, as some important genes may not be highly upregulated and could be missed by targeted approaches .

• CRISPR-Cas9 gene editing: To study specific components of the IL-22 signaling pathway through targeted knockout of receptor subunits or downstream mediators.

How can researchers effectively measure IL-22 levels in biological samples?

Multiple complementary approaches can be used:

• ELISA: Commercial kits are available for measuring IL-22 protein levels in cell culture supernatants, serum, and other biological fluids. Sensitivity typically ranges from 5-15 pg/mL.

• Flow cytometry: Intracellular cytokine staining following stimulation and protein transport inhibition to identify IL-22-producing cells.

• RT-qPCR: Measurement of IL-22 mRNA expression levels, which may precede and not always correlate with protein secretion.

• Multiplex assays: For simultaneous detection of IL-22 along with other cytokines in a sample with limited volume.

• RNA in situ hybridization: To detect IL-22 mRNA expression in tissue sections while preserving spatial context.

How does IL-22 contribute to respiratory conditions like COPD?

In COPD (Chronic Obstructive Pulmonary Disease):

• Expression pattern: IL-22 and IL-22 receptor mRNA expression and protein levels are significantly increased in both COPD patients and experimental models compared to healthy controls .

• Neutrophilic inflammation: IL-22 appears to drive neutrophilic inflammation in the lungs. Studies with IL-22-deficient (Il22−/−) mice showed reduced cigarette smoke-induced pulmonary neutrophils compared to wild-type controls .

• Pathological changes: IL-22 contributes to airway remodeling and emphysema-like alveolar enlargement. These changes were attenuated in IL-22-deficient mice .

• Lung function: IL-22 negatively impacts lung function parameters. IL-22-deficient mice demonstrated improved lung function in terms of airway resistance, total lung capacity, inspiratory capacity, forced vital capacity, and compliance .

• Mechanism: IL-22 may promote COPD pathogenesis through regulation of chemokines like CXCL1 and CXCL2, which recruit neutrophils to the lungs .

What experimental approaches can differentiate between protective and pathological roles of IL-22?

IL-22 exhibits both protective and pathological functions depending on the context. To distinguish between these roles:

• Temporal blocking studies: Administer IL-22 blocking antibodies or recombinant IL-22 binding protein (IL-22BP) at different stages of disease progression to determine when IL-22 signaling is beneficial versus detrimental.

• Cell-specific receptor deletion: Generate conditional knockout models where IL-22RA1 is deleted in specific cell types to determine which target cells mediate protective versus pathological effects.

• Dual cytokine assessment: Evaluate IL-22 in conjunction with other cytokines, particularly IL-17A, as their co-expression may determine the ultimate effect on tissue responses .

• Disease severity stratification: Compare IL-22 functions across different severity stages of a disease to identify potential shifts from protective to pathological roles.

• Transcriptomic profiling: Perform comparative transcriptomic analysis of IL-22-stimulated tissues in homeostatic versus inflammatory conditions to identify context-specific gene regulation.

What are the current knowledge gaps in IL-22 biology?

Despite increased scientific interest in IL-22 over the past decade, several knowledge gaps remain:

• Target gene identification: Many IL-22-regulated genes may have been overlooked as they are not highly upregulated. More sensitive methods are needed to identify genes regulated at lower levels .

• Context-dependent regulation: The environmental, cellular, and molecular factors that determine whether IL-22 plays a protective or inflammatory role in different disease contexts remain poorly understood .

• Integration with other pathways: How IL-22 signaling integrates with other inflammatory and tissue repair pathways is not fully elucidated.

• Post-translational modifications: The impact of different post-translational modifications on IL-22 function and signaling remains to be comprehensively characterized.

• Receptor regulation: Mechanisms controlling the expression and turnover of IL-22 receptors in different tissues during inflammation are incompletely understood.

What emerging methodologies are advancing IL-22 research?

Recent technological developments are enhancing IL-22 research:

• Single-cell analysis: Single-cell RNA sequencing and CyTOF are revealing heterogeneity in IL-22 production and response patterns within seemingly homogeneous cell populations.

• Organoid models: Three-dimensional organoid cultures enable the study of IL-22 effects on complex epithelial structures that better recapitulate in vivo tissue organization.

• Intravital imaging: Real-time visualization of IL-22-producing cells and their interactions with target cells in living tissues.

• CRISPR screens: Genome-wide or targeted screens to identify regulators of IL-22 production or response.

• Computational modeling: Integration of multi-omics data to predict context-dependent effects of IL-22 signaling in different tissues and disease states.

How has the research landscape for IL-22 evolved over the past decade?

Bibliometric analysis of IL-22 research from 2014 to 2023 reveals significant trends:

• Publication growth: The number of IL-22-related publications has steadily increased, demonstrating growing scientific interest .

• Research leaders: The United States and China are the main contributors to IL-22 research, with INSERM (France) and the University of California system being among the most active institutions .

• Publication venues: Frontiers of Immunology is both the most prolific journal for IL-22 research and the most cited .

• Research focus: Main areas of focus include immunology and cell biology, with high-frequency keywords involving molecular biology (IL-17), immune response (T cells, Th17 cells), and diseases (autoimmune diseases, cancer) .

• Emerging topics: The involvement of IL-22 in microbial populations and cancer cell spread has strong research potential and represents current hot research topics .

What are common issues when working with recombinant IL-22 and how can they be addressed?

Researchers may encounter several challenges when working with recombinant IL-22:

• Loss of activity: Recombinant IL-22 may lose activity due to improper handling or storage. Solution: Add carrier protein (0.1-0.5% BSA) to diluted protein solutions, make single-use aliquots, and avoid freeze-thaw cycles.

• Variable cellular responses: Different cell types may respond differently to IL-22 stimulation. Solution: Characterize IL-22 receptor expression on target cells before experiments and include positive control cell lines.

• Interference from endogenous factors: Cell culture components may contain factors that interfere with IL-22 activity. Solution: Use defined media when possible and include appropriate controls to account for background effects.

• Difficulty detecting low-abundance targets: Some IL-22-regulated genes may not be highly upregulated. Solution: Use sensitive detection methods and consider longer stimulation timepoints to capture secondary effects.

• Species-specificity issues: Human and mouse IL-22 may have different potencies and receptor affinities. Solution: Use species-matched recombinant proteins and validate cross-reactivity when necessary.

What experimental controls are essential when studying IL-22 functions?

Critical controls include:

• Receptor expression verification: Confirm that target cells express IL-22RA1 and IL-10RB by qPCR, flow cytometry, or western blotting.

• Heat-inactivated protein control: Compare responses to active vs. heat-denatured IL-22 to confirm specificity.

• Receptor blocking: Include conditions with IL-22 receptor blocking antibodies or soluble receptors to confirm specificity of observed effects.

• Dose-response assessment: Perform serial dilutions of IL-22 to establish dose-dependent effects and determine optimal concentrations.

• Positive control cell line: Include a well-characterized IL-22-responsive cell line such as HepG2 (liver) or HT29 (intestinal) cells as a technical positive control.

• Genetic validation: When possible, include cells from IL-22RA1 knockout models or use siRNA/CRISPR to confirm receptor dependency.

What are promising therapeutic applications of IL-22 research?

Based on current understanding, several therapeutic avenues show promise:

• Tissue regeneration: Harnessing IL-22's role in epithelial cell regeneration to promote healing in conditions like inflammatory bowel disease or acute lung injury.

• Targeted blockade: Selective blocking of IL-22 signaling in conditions where it drives pathology, such as COPD and certain autoimmune conditions .

• Combinatorial approaches: Targeting IL-22 alongside other cytokines (particularly IL-17) to address complex inflammatory conditions.

• Precision medicine: Developing biomarkers to identify patients likely to benefit from IL-22 modulation based on disease subtype and stage.

• Enhanced delivery methods: Developing tissue-specific delivery systems for IL-22 or IL-22 inhibitors to maximize therapeutic efficacy while minimizing systemic effects.

How can researchers better understand the dichotomy of IL-22 function in different disease contexts?

To address the complex dual nature of IL-22:

• Temporal studies: Detailed time-course experiments examining IL-22's role throughout disease progression, from initiation through resolution phases.

• Microenvironment characterization: Comprehensive analysis of the tissue microenvironment factors that influence whether IL-22 promotes protection or pathology.

• Receptor regulation focus: Investigation of how IL-22 receptor expression and signaling are regulated in different disease contexts.

• Systems biology approaches: Integration of transcriptomic, proteomic, and metabolomic data to build predictive models of IL-22 function in different contexts.

• Single-cell resolution studies: Analysis of cell-specific responses to IL-22 within complex tissues to identify differential responders that may explain contradictory outcomes.

Table of Methods for Measuring IL-22 Production and Activity