Cytokines vs Chemokines- Definition and 8 Major Differences

Cytokines and chemokines are two types of molecules that play important roles in the immune system. They are both secreted by various cells in response to different stimuli, such as infection, inflammation, injury, or stress. They act as messengers that communicate with other cells and influence their behavior, such as growth, differentiation, activation, migration, and death .

Cytokines are a broad family of proteins that can affect many aspects of immunity, such as innate and adaptive responses, hematopoiesis, wound healing, and tissue homeostasis. They include several subfamilies, such as interleukins (ILs), interferons (IFNs), tumor necrosis factors (TNFs), colony-stimulating factors (CSFs), and transforming growth factors (TGFs). Each cytokine has a specific receptor on the target cell that binds to it and triggers a signal transduction pathway that leads to a cellular response .

Chemokines are a special type of cytokines that are mainly involved in directing the movement of cells, especially white blood cells (leukocytes), to the sites of infection or damage. They create a concentration gradient that attracts the cells along it towards the source of chemokine production. They also regulate the trafficking and positioning of immune cells within the tissues and organs. Chemokines are classified into four subfamilies based on the arrangement of cysteine residues in their structure: CXC, CC, CX3C, and XC .

Cytokines and chemokines are essential for the coordination and regulation of immune responses. However, they can also cause harmful effects if they are overproduced or dysregulated. For example, excessive or chronic inflammation can result from an imbalance of pro-inflammatory and anti-inflammatory cytokines. Similarly, abnormal chemokine expression can contribute to autoimmune diseases, allergies, cancer, and viral infections . Therefore, understanding the functions and interactions of cytokines and chemokines is important for developing new therapies for various immune-related disorders.

Cytokines and chemokines are both types of signaling molecules that are produced by cells of the immune system and other tissues. They play important roles in regulating inflammation, immunity, cell growth, differentiation, and migration. However, they have some distinct differences in their structure, function, and classification.

• Structure: Cytokines are a diverse group of proteins that vary in size, shape, and amino acid sequence. They can be classified into several families based on their structural features, such as interleukins, interferons, tumor necrosis factors, and colony-stimulating factors. Chemokines are a subset of cytokines that share a common structural motif of four cysteine residues that form two disulfide bonds. They can be classified into four subfamilies based on the arrangement of these cysteines: CXC, CC, C, and CX3C.
• Function: Cytokines have multiple functions that depend on the type of cytokine, the target cell, and the context of the signal. They can modulate the activation, proliferation, differentiation, and survival of various immune cells, such as T cells, B cells, macrophages, and dendritic cells. They can also affect the expression of genes involved in inflammation, wound healing, tissue repair, and angiogenesis. Chemokines have a more specific function of inducing the chemotaxis (directed movement) of immune cells to sites of infection or injury. They bind to specific receptors on the surface of leukocytes (white blood cells) and activate intracellular signaling pathways that regulate the cytoskeleton and cell motility.
• Classification: Cytokines are classified based on their source (autocrine, paracrine, or endocrine), their target (pleiotropic or specific), their mode of action (synergistic or antagonistic), and their receptor type (membrane-bound or soluble). Chemokines are classified based on their structural subfamily (CXC, CC, C, or CX3C), their receptor specificity (homeostatic or inflammatory), and their target cell type (neutrophils, monocytes/macrophages, lymphocytes, or eosinophils/basophils).

These are some of the main differences between cytokines and chemokines. In the following sections, we will explore more details about their characteristics and compare them in terms of cell signaling and chemotaxis.

Cytokines are a large group of proteins that are secreted by various cells of the immune system and other tissues. They act as signaling molecules that regulate the immune response, inflammation, wound healing, hematopoiesis, and other biological processes. Cytokines can have autocrine, paracrine, or endocrine effects, depending on whether they act on the same cell that produced them, on nearby cells, or on distant cells through the bloodstream.

Cytokines can be classified into several families based on their structure, function, and receptor binding. Some of the major cytokine families are:

• Interleukins (ILs): These are cytokines that are mainly produced by and act on leukocytes (white blood cells). They have diverse roles in immune regulation, such as stimulating or inhibiting the proliferation, differentiation, and activation of various immune cells. There are currently more than 40 interleukins identified, each with a specific receptor and function. For example, IL-1 is a pro-inflammatory cytokine that induces fever and inflammation; IL-2 is a growth factor for T cells and natural killer (NK) cells; IL-4 is an anti-inflammatory cytokine that promotes the differentiation of B cells into plasma cells and T cells into Th2 cells; IL-10 is an anti-inflammatory cytokine that inhibits the production of pro-inflammatory cytokines by macrophages and dendritic cells; and IL-17 is a pro-inflammatory cytokine that stimulates the production of chemokines and other inflammatory mediators by epithelial cells and fibroblasts.
• Interferons (IFNs): These are cytokines that are mainly produced by and act on cells infected by viruses or other intracellular pathogens. They have antiviral, antiproliferative, and immunomodulatory effects. There are three types of interferons: type I (IFN-α and IFN-β), type II (IFN-γ), and type III (IFN-λ). Type I interferons are produced by most cell types in response to viral infection or toll-like receptor (TLR) stimulation. They induce the expression of genes that inhibit viral replication and enhance the antigen presentation and cytotoxicity of infected cells. Type II interferon is produced by activated T cells and NK cells. It activates macrophages to kill intracellular pathogens and enhances the differentiation of T cells into Th1 cells. Type III interferons are produced by epithelial cells in response to viral infection or TLR stimulation. They have similar antiviral effects as type I interferons but bind to different receptors.
• Tumor necrosis factor (TNF): This is a cytokine that is mainly produced by activated macrophages, monocytes, and T cells. It has pro-inflammatory, cytotoxic, and apoptotic effects. TNF can induce the expression of adhesion molecules, chemokines, and other inflammatory mediators by endothelial cells and other cell types. It can also induce cell death in tumor cells and infected cells by activating caspases and other pathways. TNF can also regulate metabolic processes such as lipolysis, insulin resistance, and cachexia.
• Colony-stimulating factors (CSFs): These are cytokines that are mainly produced by bone marrow stromal cells, endothelial cells, fibroblasts, and other cell types. They stimulate the proliferation, differentiation, survival, and function of hematopoietic stem cells and progenitor cells. There are four major CSFs: granulocyte-macrophage CSF (GM-CSF), granulocyte CSF (G-CSF), macrophage CSF (M-CSF), and erythropoietin (EPO). GM-CSF stimulates the production of granulocytes (neutrophils, eosinophils, basophils) and monocytes/macrophages; G-CSF stimulates the production of neutrophils; M-CSF stimulates the production of monocytes/macrophages; and EPO stimulates the production of erythrocytes (red blood cells).
• Growth factors: These are cytokines that are mainly produced by various cell types in response to growth signals or tissue damage. They stimulate the growth, survival, migration, differentiation, and function of various cell types. Some examples of growth factors are: vascular endothelial growth factor (VEGF), which stimulates angiogenesis (the formation of new blood vessels); platelet-derived growth factor (PDGF), which stimulates wound healing and fibrosis; nerve growth factor (NGF), which stimulates neuronal survival and differentiation; epidermal growth factor (EGF), which stimulates epithelial cell proliferation and differentiation; and insulin-like growth factor (IGF), which stimulates metabolic processes and growth in various tissues.

These are some of the main characteristics of cytokines. However, cytokines are not rigidly defined by their structure or function, and there is considerable overlap and redundancy among them. Moreover, cytokines can have different effects depending on the context, such as the type, dose, duration, and combination of cytokines, the type and state of the target cells, and the presence of other factors. Therefore, cytokines are best understood as a complex network of communication among cells that regulates various aspects of physiology and pathology.

Chemokines are a type of cytokines that have a specific function: they attract and activate leukocytes (white blood cells) to sites of inflammation, infection, or injury. Chemokines are small proteins (8-10 kDa) that have a conserved structure of four cysteine residues that form two disulfide bonds. Based on the arrangement of these cysteines, chemokines are classified into four subfamilies: CC, CXC, CX3C, and XC. Each subfamily has different receptors and functions.

Chemokines are produced by various cells, such as macrophages, dendritic cells, endothelial cells, fibroblasts, epithelial cells, and lymphocytes. They are secreted in response to stimuli such as cytokines, pathogens, or tissue damage. Chemokines bind to specific G-protein-coupled receptors (GPCRs) on the surface of leukocytes and activate intracellular signaling pathways that induce chemotaxis (directed cell movement), adhesion, migration, activation, and differentiation of the leukocytes.

Chemokines play an important role in both innate and adaptive immunity. They recruit and regulate the trafficking of neutrophils, monocytes, eosinophils, basophils, mast cells, natural killer cells, dendritic cells, and T and B lymphocytes to the sites where they are needed. They also modulate the expression of adhesion molecules and co-stimulatory molecules on leukocytes and endothelial cells, which facilitate the interactions between them. Chemokines also influence the polarization and effector functions of T helper cells and cytotoxic T cells.

Chemokines are also involved in non-immunological processes, such as angiogenesis (formation of new blood vessels), wound healing, tissue remodeling, embryonic development, and neurogenesis (formation of new neurons). They can also mediate pathological conditions, such as chronic inflammation, autoimmune diseases, allergies, asthma, atherosclerosis, cancer metastasis, and viral infections. Therefore, chemokines are potential targets for therapeutic interventions in various diseases.

Cytokines and chemokines are both involved in cell signaling, which is the process of communication between cells. Cell signaling can be classified into four types: autocrine, paracrine, endocrine, and juxtacrine.

• Autocrine signaling occurs when a cell produces and responds to its own signal. For example, some T cells secrete and bind to interleukin-2 (IL-2), a cytokine that stimulates their proliferation and activation.
• Paracrine signaling occurs when a cell produces a signal that affects nearby cells. For example, macrophages secrete tumor necrosis factor-alpha (TNF-alpha), a cytokine that induces inflammation and apoptosis in neighboring cells.
• Endocrine signaling occurs when a cell produces a signal that travels through the bloodstream to reach distant cells. For example, erythropoietin (EPO), a cytokine that stimulates red blood cell production, is secreted by the kidney and acts on the bone marrow.
• Juxtacrine signaling occurs when a cell produces a signal that is presented on its surface and binds to receptors on adjacent cells. For example, B cells express CD40 ligand (CD40L), a cytokine that activates T cells through direct contact.

Cytokines and chemokines can act as autocrine, paracrine, or endocrine signals, depending on their concentration, receptor expression, and target cell type. However, chemokines are more likely to act as paracrine signals than cytokines, because they are mainly involved in attracting and activating leukocytes to sites of inflammation and infection. Chemokines can also form gradients that guide the directional movement of cells, a process called chemotaxis.

Cytokines and chemokines can also act as juxtacrine signals, but this is less common than the other types of signaling. One example of juxtacrine signaling by cytokines is the interaction between CD40L on T cells and CD40 on B cells, which is essential for antibody production. One example of juxtacrine signaling by chemokines is the interaction between CX3CL1 (fractalkine) on endothelial cells and CX3CR1 on monocytes, which mediates adhesion and transmigration of monocytes across the blood vessel wall.

In summary, cytokines and chemokines are both involved in cell signaling, but they differ in their modes of action. Cytokines can act as autocrine, paracrine, endocrine, or juxtacrine signals, depending on the context. Chemokines are more likely to act as paracrine signals that induce chemotaxis of leukocytes to sites of inflammation and infection. Chemokines can also act as juxtacrine signals that mediate cell-cell interactions.

Cytokines and chemokines are both involved in the regulation of cell movement, but they have different mechanisms and effects. Cytokines can induce chemotaxis, which is the directed migration of cells towards a gradient of chemical signals. Chemokines are a subset of cytokines that specialize in chemotaxis and attract specific types of cells to sites of inflammation, infection, or injury.

Cytokines can induce chemotaxis by binding to receptors on the surface of target cells and activating intracellular signaling pathways that alter the cytoskeleton and the expression of adhesion molecules. Cytokines can also modulate the responsiveness of target cells to chemokines by upregulating or downregulating their chemokine receptors. For example, interferon-gamma (IFN-gamma) can increase the expression of CXCR3, a receptor for the chemokine CXCL10, on T cells and natural killer (NK) cells, enhancing their migration to inflamed tissues.

Chemokines can induce chemotaxis by forming concentration gradients in the extracellular space and binding to specific G protein-coupled receptors (GPCRs) on target cells. Chemokines can also form complexes with glycosaminoglycans (GAGs) on the surface of endothelial cells or extracellular matrix (ECM) proteins, creating a haptotactic gradient that guides cell movement along a substrate. Chemokines can also activate intracellular signaling pathways that regulate the cytoskeleton and the adhesion molecules, as well as other cytokine receptors and effector molecules. For example, CCL2 can bind to CCR2 on monocytes and macrophages, triggering their migration to sites of inflammation and infection.

Cytokines and chemokines have different effects on cell movement depending on the context and the combination of signals. Cytokines can have positive or negative effects on chemotaxis, depending on the type and dose of cytokine, the type and state of target cell, and the presence or absence of other cytokines or chemokines. For example, tumor necrosis factor-alpha (TNF-alpha) can enhance or inhibit the chemotaxis of neutrophils depending on its concentration and the presence of other inflammatory mediators. Chemokines can also have positive or negative effects on chemotaxis, depending on the type and concentration of chemokine, the type and expression level of chemokine receptor, and the presence or absence of other chemokines or cytokines. For example, CXCL12 can attract or repel CXCR4-expressing cells depending on its gradient and the presence of other CXCR4 ligands.

In summary, cytokines and chemokines are both involved in the regulation of cell movement, but they have different mechanisms and effects. Cytokines can induce chemotaxis by binding to receptors on target cells and modulating their responsiveness to chemokines. Chemokines are a subset of cytokines that specialize in chemotaxis by forming gradients in the extracellular space and binding to specific GPCRs on target cells. Cytokines and chemokines can have positive or negative effects on cell movement depending on the context and the combination of signals.

Besides the definition and the cell signaling, there are other differences between cytokines and chemokines that are worth mentioning. Here are some of them:

• Structure: Cytokines are a diverse group of proteins that can have different structures, such as globular, helical, or dimeric. Chemokines, on the other hand, are a subset of cytokines that share a common structure of four cysteine residues forming two disulfide bonds. Chemokines can be classified into four subfamilies based on the arrangement of these cysteines: CXC, CC, C, and CX3C.
• Receptors: Cytokines can bind to various types of receptors on the cell surface, such as cytokine receptors, immunoglobulin superfamily receptors, tumor necrosis factor receptors, or toll-like receptors. Chemokines bind to a specific family of receptors called chemokine receptors, which belong to the G protein-coupled receptor (GPCR) superfamily. Chemokine receptors are named according to the subfamily of chemokines they bind to, such as CXCR for CXC chemokines or CCR for CC chemokines.
• Function: Cytokines have a wide range of functions in the immune system and beyond. They can regulate inflammation, immunity, hematopoiesis, wound healing, tissue repair, development, differentiation, and apoptosis. Chemokines have a more specialized function in mediating the migration and activation of leukocytes (white blood cells) in response to infection or injury. Chemokines can also modulate angiogenesis (blood vessel formation), tumor growth, and metastasis.
• Expression: Cytokines can be expressed by various types of cells, such as immune cells (e.g., macrophages, T cells, B cells), epithelial cells, endothelial cells, fibroblasts, or adipocytes. Chemokines are mainly expressed by immune cells and endothelial cells at sites of inflammation or infection. However, some chemokines can also be constitutively expressed by certain tissues (e.g., lymph nodes, thymus, bone marrow) to maintain the homeostasis of leukocyte trafficking.
• Regulation: Cytokines can be regulated at different levels: transcriptional (e.g., by transcription factors or epigenetic modifications), post-transcriptional (e.g., by microRNAs or RNA-binding proteins), translational (e.g., by ribosomal proteins or initiation factors), post-translational (e.g., by proteases or glycosylation), or secretion (e.g., by vesicles or exosomes). Chemokines are mainly regulated at the transcriptional level by various stimuli, such as cytokines (e.g., TNF-alpha or IL-1 beta), pathogens (e.g., bacteria or viruses), or hypoxia (low oxygen levels).
• Redundancy: Cytokines can have redundant or overlapping functions with other cytokines. For example, IL-2 and IL-15 can both stimulate the proliferation and survival of T cells. Chemokines can also have redundant functions with other chemokines. For example, CXCL8 and CXCL1 can both recruit neutrophils to sites of inflammation.
• Pleiotropy: Cytokines can have pleiotropic effects on different cell types or tissues. For example, IL-6 can induce fever and acute phase response in the liver, stimulate B cell differentiation and antibody production in the lymph nodes, and inhibit T cell proliferation and function in the spleen. Chemokines can also have pleiotropic effects on different cell types or tissues. For example, CXCL12 can attract hematopoietic stem cells to the bone marrow, promote angiogenesis in the heart and brain, and inhibit HIV infection in the lymphoid organs.

Cytokines and chemokines are both small proteins that are secreted by cells and involved in inflammation and cell signaling . However, they have some important differences that distinguish them from each other. Here is a summary of the 8 major differences between cytokines and chemokines:

• Cytokines are a general category of messenger molecules, while chemokines are a specific type of cytokines that have the ability to induce chemotaxis, which is the guiding of cell movement towards a target location .
• Cytokines have a broader range of functions, such as regulating immunity, hematopoiesis, growth, differentiation, and apoptosis, while chemokines mainly focus on white blood cell migration to damaged or infected body parts .
• Cytokines can be secreted by various types of cells in the body, such as macrophages, lymphocytes, endothelial cells, fibroblasts, and epithelial cells, while chemokines are mainly secreted by activated leukocytes and endothelial cells .
• Cytokines can be classified into several superfamilies based on their structure and function, such as interleukins (ILs), interferons (IFNs), colony-stimulating factors (CSFs), tumor necrosis factors (TNFs), and transforming growth factors (TGFs), while chemokines are classified into four subfamilies based on the arrangement of their cysteine residues, such as CC, CXC, CX3C, and XC .
• Cytokines can act in an autocrine, paracrine, or endocrine manner, meaning they can bind to receptors on the same cell that secreted them, on nearby cells, or on distant cells through the bloodstream, while chemokines mainly act in a paracrine manner, meaning they bind to receptors on nearby cells that are attracted by the concentration gradient .
• Cytokines can have either pro-inflammatory or anti-inflammatory effects depending on the type and context of their secretion, while chemokines are mostly pro-inflammatory as they recruit leukocytes to the site of inflammation .
• Cytokines can have either synergistic or antagonistic interactions with other cytokines depending on the type and context of their secretion, while chemokines mostly have synergistic interactions with other chemokines as they cooperate to enhance leukocyte migration .
• Cytokines can have either pleiotropic or redundant effects depending on the type and context of their secretion, meaning they can affect multiple cell types or have similar functions as other cytokines, while chemokines mostly have specific effects depending on the type of receptor they bind to .

Cytokines and chemokines have important roles in various physiological and pathological processes, such as immunity, inflammation, wound healing, cancer, and infectious diseases . They can be used as biomarkers, therapeutic targets, or drugs for different conditions .

Some examples of applications of cytokines and chemokines are:

• Interferons are cytokines that have antiviral, antiproliferative, and immunomodulatory effects. They are used to treat viral infections, such as hepatitis B and C, and some cancers, such as leukemia and melanoma.
• Interleukins are cytokines that regulate the growth and differentiation of various immune cells. They are used to treat autoimmune diseases, such as rheumatoid arthritis and psoriasis, and some cancers, such as lymphoma and kidney cancer.
• Colony-stimulating factors are cytokines that stimulate the production of blood cells. They are used to treat anemia, neutropenia, and thrombocytopenia caused by chemotherapy or bone marrow transplantation.
• Tumor necrosis factors are cytokines that induce cell death and inflammation. They are used to treat inflammatory diseases, such as Crohn`s disease and ulcerative colitis, and some cancers, such as melanoma and sarcoma.
• Transforming growth factors are cytokines that regulate cell growth, differentiation, and migration. They are involved in tissue repair, fibrosis, angiogenesis, and tumorigenesis. They can be used as inhibitors or enhancers of these processes depending on the context.
• Chemokines are cytokines that attract and activate leukocytes. They are involved in inflammatory responses, wound healing, angiogenesis, and metastasis. They can be used as biomarkers or therapeutic targets for various diseases, such as asthma, atherosclerosis, arthritis, diabetes, and cancer.

Comparison of therapeutic applications of cytokines and chemokines

Cytokines and chemokines have been explored as potential therapeutic agents for various diseases, such as cancer, autoimmune disorders, infections, and inflammation . However, their use is limited by several challenges, such as toxicity, instability, immunogenicity, and redundancy. Moreover, the effects of cytokines and chemokines are context-dependent and may vary depending on the target cells, tissues, and organs.

Some examples of cytokines that have been used or investigated for clinical applications are:

• Interferons (IFNs): These are cytokines that have antiviral, antiproliferative, and immunomodulatory effects. They have been approved for the treatment of hepatitis B and C, multiple sclerosis, hairy cell leukemia, melanoma, and Kaposi`s sarcoma.
• Interleukins (ILs): These are cytokines that regulate the growth and differentiation of various immune cells. They have been used for the treatment of rheumatoid arthritis (IL-1 receptor antagonist), anemia (IL-11), and cancer (IL-2 and IL-12).
• Colony-stimulating factors (CSFs): These are cytokines that stimulate the production of blood cells from hematopoietic stem cells. They have been used for the treatment of neutropenia (granulocyte-CSF), anemia (erythropoietin), and thrombocytopenia (thrombopoietin).
• Tumor necrosis factor (TNF): This is a cytokine that has pro-inflammatory and cytotoxic effects. It has been used for the treatment of cancer (TNF-alpha) and inflammatory bowel disease (TNF-alpha inhibitor).
• Transforming growth factor (TGF): This is a cytokine that has anti-inflammatory and immunosuppressive effects. It has been investigated for the treatment of fibrosis, wound healing, and graft-versus-host disease.

Some examples of chemokines that have been used or investigated for clinical applications are:

• CXCL8: This is a chemokine that attracts neutrophils and other inflammatory cells to the site of infection or injury. It has been used for the treatment of chronic wounds and ulcers.
• CXCL12: This is a chemokine that regulates the migration and homing of hematopoietic stem cells. It has been used for the enhancement of stem cell transplantation and mobilization.
• CCL2: This is a chemokine that recruits monocytes and macrophages to the site of inflammation or tissue damage. It has been investigated for the treatment of atherosclerosis, rheumatoid arthritis, and neuropathic pain.
• CCL5: This is a chemokine that activates T cells and natural killer cells. It has been investigated for the treatment of HIV infection, cancer, and asthma.
• CXCR4: This is a chemokine receptor that binds to CXCL12 and mediates various cellular functions. It has been targeted by drugs such as plerixafor and AMD3100 for the treatment of HIV infection, stem cell mobilization, and cancer.

In summary, cytokines and chemokines have diverse roles in the immune system and can be used as therapeutic agents for various diseases. However, their clinical application is limited by several challenges and requires careful optimization and evaluation.

Comparison of cytokine and chemokine receptors

Another difference between cytokines and chemokines is the type of receptors they bind to on the target cells. Cytokine receptors are a large and diverse family of transmembrane proteins that can be classified into six subfamilies based on their structural features. These subfamilies are:

• Type I cytokine receptors (e.g., IL-2R, IL-4R, IL-6R)
• Type II cytokine receptors (e.g., IFNAR, IFNGR, IL-10R)
• Immunoglobulin superfamily cytokine receptors (e.g., IL-1R, IL-18R, TLRs)
• Tumor necrosis factor receptor superfamily (e.g., TNFR, Fas, CD40)
• Interleukin-17 receptor family (e.g., IL-17RA, IL-17RB, IL-17RC)
• Chemokine receptors (e.g., CCR1, CXCR4, CX3CR1)

Chemokine receptors are a specific subfamily of cytokine receptors that belong to the G protein-coupled receptor (GPCR) superfamily. They have seven transmembrane domains and couple to G proteins to activate intracellular signaling pathways. Chemokine receptors are named according to the type of chemokines they bind to: CXC, CC, CX3C, or XC. For example, CXCR4 is a receptor for CXCL12 (also known as SDF-1), and CCR5 is a receptor for CCL3 (also known as MIP-1α), CCL4 (also known as MIP-1β), and CCL5 (also known as RANTES).

The binding of cytokines and chemokines to their respective receptors triggers different cellular responses depending on the context and the cell type. For instance, cytokines can induce proliferation, differentiation, activation, survival, or apoptosis of immune cells. Chemokines can induce chemotaxis, adhesion, migration, polarization, or degranulation of leukocytes. Both cytokines and chemokines can also modulate the expression of other cytokines and chemokines, creating a complex network of interactions that regulate the immune system .

In summary, cytokines and chemokines differ in their receptor types: cytokines bind to various subfamilies of transmembrane proteins that have different structural features and signaling mechanisms, while chemokines bind to a specific subfamily of GPCRs that have seven transmembrane domains and activate G proteins. The binding of cytokines and chemokines to their receptors leads to different cellular responses that mediate and modulate the immune system.

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