The Evolution of Cytokine Assays: Advances and Applications in Medical Research
Cytokines are low molecular weight soluble proteins secreted by different cell types, including stromal cells, mast cells, natural killer cells, macrophages, lymphocytes, etc. They are key players in immune response and are mediators in immune communication networks. Cytokines regulate immune cell growth, responsiveness, and maturation. Besides, they are important health indicators. Multiple cells may secrete a single cytokine and can produce several biological activities. Besides, cytokine levels in biological fluids such as blood, serum, plasma, sweat, etc, offer deep insights into the diagnosis, prognosis, and stage of different diseases.
In practice, detecting cytokines is challenging due to their presence in trace amounts, short half-lives, and dynamic secretion processes. Cytokines are present in complex networks to modulate immune responses. Hence, cytokines may have synergistic, additive, or antagonistic influence on biological systems. The innately complex nature of biological processes makes cytokine detection difficult. Today, PCR and ELISA are the most commonly employed methods for detecting and quantifying cytokines in biological matrices. However, these methods are time-consuming, highly complex, and have a longer sample preparation period. Hence, novel techniques such as biosensors are increasingly explored in cytokine quantification.
The current article explores new advanced cytokine assays and their applications in medical research. However, robust assay validation and optimization are necessary for generating reliable, reproducible, and accurate results.
Cytokine assays for accelerating medical research and development.
Cytokines have demonstrated participation in hematopoietic development, immune response regulation, cell-to-cell communication, and responses to inflammatory stimuli and infectious agents. Cytokines are critical mediators of interactions among cell types and their dysregulation, resulting in disease pathogenesis. Generally, cytokines are undetectable in tissues or body fluids because of their presence at low levels. Hence, their elevated levels in body fluids indicate cytokine activation associated with disease progression or inflammation.
Cytokines associated with chronic and acute diseases are distinct. Cytokines may be present in later or early stages of disease. Consistent elevated cytokine levels in specific diseases may suggest that therapy against cytokines may prove beneficial. Hence, evaluating cytokines in several biological fluids may prove advantageous, especially for employing cytokines as therapeutic agents. Today, multiple cytokine assays are available to study cytokines in biological samples and establish therapeutic potential.
Cytokines are biologically complex. All cytokines can interact with multiple cell targets via receptors on the target cell surface. Cell surface cytokine binding results in the signaling and synthesis of new RNA and protein. Besides, they can work as cascades or networks of interacting cytokines that can induce each other. Moreover, cytokines regulate their production through paracrine, juxtacrine, or autocrine pathways to induce biological effects. Hence, they are potent mediators of physiological alterations with the potential to cause tissue damage.
Since cytokine events are common in multiple pathological conditions, multi-cytokine profiling could be more clinically relevant than estimating a single cytokine. Today, research studies focused on cytokine assessments have resulted in a consensus of simultaneous cytokine quantification in a single study sample. Hence, cytokine assays have emerged as a robust replacement for traditional biological assays.
Cytokine assays
In vitro and in vivo approaches are traditionally being used in cytokine quantification. In vitro cytokine quantification is effective and flexible. These methods test multiple study samples such as tissues, cells, and body fluids. Today, in vitro cytokine assays include PCR, ELISA, and advanced biosensors such as POC testing. On the other hand, in vivo cytokine quantification involves studying complex inflammatory and regulatory networks. In vitro approaches include assessments to study cytokine trafficking and the regulation of their networks. However, inappropriate storage and processing generate inaccurate results. Besides, non-homogenous cytokine distribution makes localized in vivo detection critical to understanding cytokine release and expression dynamics. After the success of electrochemical immunosensors, optical fiber-based devices are now being explored for cytokine detection.
The ultralow cytokine concentration and dynamic and transient nature of cytokine secretion make cytokine detection and quantification challenging. Biosensors are analytical devices that integrate nanotechnology with physicochemical detectors. These systems have shown significant potential in cytokine sensing. These biosensors employ a wide range of signal readouts to quantify extracellular and intracellular cytokines in real-time. The types of signal readouts include fluorescence immunoassays, electrochemical-based methods, surface plasmon resonance detection, colorimetric, surface-enhanced Raman spectroscopy, and CRISPR/Cas signal-amplification linked immunosorbent assay.
Additionally, multiple commercial assay systems are available to quantify cytokines in clinical study samples. Traditional ELISA assays can detect a single cytokine in complex study samples. Besides, commercial multiplex technologies such as flow cytometry-based or Luminex-based assays are widely employed in cytokine quantification. Most of these methods profile multiple cytokines in small sample volumes. These advanced assay systems offer several benefits, such as reduced assay time, reduced study sample volume, and a broad dynamic assay range.
Conclusion
Cytokine detection and quantification is highly complex yet offers deep insights into disease and disorder diagnosis and treatment. Today, several methods have shown the potential to deliver sensitive and reliable cytokine data through multiple signal readouts for in vivo and in vitro applications. However, adequate assay development remains critical for instilling confidence in generated results.
