Cytokines and Immune Response: Key Concepts and Functions

What are cytokines and their primary function?

Cytokines are chemical messengers that influence the activities of other cells, regulating immune responses and acting as growth factors for hematopoietic cells.

What is autocrine stimulation?

Autocrine stimulation refers to a cytokine affecting the same cell that secreted it.

What is paracrine stimulation?

Paracrine stimulation involves a cytokine affecting a target cell in close proximity.

What is endocrine stimulation in relation to cytokines?

Endocrine stimulation refers to systemic effects, which are generally exceptions for cytokines.

What does pleiotropy mean in the context of cytokines?

Pleiotropy means a single cytokine can have many different functions.

What is redundancy in cytokine function?

Redundancy refers to different cytokines having similar effects.

What is a cytokine network?

A cytokine network is when one cytokine stimulates the production of another cytokine that has similar or overlapping activity.

What characterizes the innate immune response?

The innate immune response is non-specific, activated within hours of first contact, and does not significantly increase in efficacy upon repeated exposure.

What role do cytokines play in the innate immune response?

Cytokines produced during the innate immune response increase vascular permeability, alter adhesive properties of endothelial cells, and recruit additional immune components to the site of infection.

What is the adaptive immune response?

The adaptive immune response is specific immunity that recognizes a vast number of targets and becomes effective 2 to 4 days after first exposure, with immune memory for faster protection upon re-exposure.

Which cytokine is primarily produced by macrophages and monocytes in response to bacteria?

Interleukin-1 (IL-1) is produced by macrophages and monocytes in response to bacterial lipopolysaccharides.

What are the effects of IL-1 in the immune response?

IL-1 acts as a pro-inflammatory mediator, enhances cytotoxicity of NK cells, stimulates B cell proliferation, and can induce fever.

What is Tumor Necrosis Factor (TNF) and its primary role?

TNF is a major mediator of innate defense against gram-negative bacteria and can trigger apoptosis in target cells.

What triggers the secretion of TNF?

The major trigger for TNF secretion is lipopolysaccharides (LPS) from gram-negative bacteria.

What are the systemic effects of TNF when secreted in large amounts?

In large amounts, TNF acts as a systemic mediator, enhancing leukocyte activity and contributing to fever.

What is an endogenous pyrogen?

An endogenous pyrogen is a substance, such as TNF, that induces fever.

What cytokines does TNF stimulate the secretion of?

TNF stimulates the secretion of other pro-inflammatory cytokines, including IL-1, IL-6, and IL-8.

How does IL-1 affect neutrophils?

IL-1 acts as a chemotactic agent, increasing neutrophils at the site of infection.

What are the effects of IL-1 on blood pressure and heart rate?

IL-1 can cause hypoglycemia, hypotension, depressed myocardial contractility, and increased heart rate.

What is the role of IL-2 in T cells?

IL-2 induces the expression of IL-2 receptors (CD25) in T cells and promotes their proliferation and differentiation.

What is the significance of immune memory in the adaptive immune response?

Immune memory allows for a more rapid and effective response upon re-exposure to the same infectious agent.

What is the difference between innate and adaptive immune responses?

The innate immune response is non-specific and immediate, while the adaptive immune response is specific and takes longer to become effective.

What role does TNF play in the acute phase response?

TNF induces the acute phase response, which includes an increased sedimentation rate.

What are the effects of high levels of TNF?

High levels of TNF can cause metabolic alterations, depress myocardial contractility, relax vascular smooth muscle, and promote intravascular coagulation.

What condition is caused by septic shock related to TNF?

Septic shock is caused by huge amounts of TNF in response to gram-negative bacterial infection, leading to decreased blood pressure and disseminated intravascular coagulation (DIC).

What is cachexia and how is it related to TNF?

Cachexia is a catabolic state resulting in the wasting of fat and muscle tissue, produced by chronic TNF.

What cells produce Interleukin-6 (IL-6)?

IL-6 is made by mononuclear phagocytes, vascular endothelial cells, and fibroblasts.

When does IL-6 appear during an infection?

IL-6 appears later in the infection cascade, after TNF and IL-1.

What are the primary functions of IL-6?

IL-6 is a primary mediator of the acute phase response, signals for enhanced fibrinogen synthesis by the liver, and acts as a growth factor for activated B cells and plasma cells.

What are chemokines?

Chemokines are chemotactic cytokines that enhance motility and promote the migration of leukocytes to sites of inflammation.

What distinguishes the C-C subgroup of chemokines?

The C-C subgroup is produced primarily by activated T lymphocytes and leukocytes other than neutrophils.

What distinguishes the C-X-C subgroup of chemokines?

The C-X-C subgroup is produced primarily by mononuclear phagocytes, endothelial cells, fibroblasts, and megakaryocytes.

What is the role of Transforming Growth Factor-beta (TGF-β) in immune response?

TGF-β functions as both an activator and an inhibitor of proliferation, regulates CD8 expression in thymocytes, and acts as an anti-inflammatory factor for mature T cells.

How does TGF-β affect macrophages?

TGF-β inhibits the activation of macrophages and regulates the growth of various somatic cell types.

What are Type I Interferons and their role in the immune response?

Type I Interferons (IFN-α, IFN-β, IFN-γ) interfere with viral replication and enhance the innate immune response.

What is the primary production source of IFN-α?

IFN-α is primarily produced by plasmacytoid dendritic cells in response to viral infections.

What are the effects of Type I Interferons on virally infected cells?

They inhibit viral replication, increase the ability of natural killer cells to kill infected cells, and enhance the expression of class I MHC.

What cytokines are involved in adaptive immune responses?

Cytokines involved in adaptive immune responses include IL-2, which is crucial for T cell proliferation.

What is the function of IL-2 in T cell activation?

IL-2 stimulates activated T cells to proliferate and amplifies the cellular immune response.

What is the role of Th1 and Th2 cells in the immune response?

Th1 cells are responsible for cell-mediated immunity and produce IL-2 and IFN-γ, while Th2 cells produce IL-4 and IL-5, aiding in B cell activation.

How does IL-2 affect surrounding cells?

IL-2 acts not only on the cell that produced it but also on nearby cells, amplifying the immune response.

What is the significance of the acute phase response?

The acute phase response is a rapid inflammatory response that helps the body fight infection and heal.

What is disseminated intravascular coagulation (DIC)?

DIC is a serious condition characterized by the widespread activation of the clotting cascade, leading to the formation of blood clots throughout the small blood vessels.

What is the relationship between TNF and DIC?

TNF can impair the anticoagulant properties of endothelial cells, contributing to the development of DIC.

What is the primary function of interferon-gamma (INF-y)?

To activate macrophages and enhance their ability to kill tumor cells and virally infected cells.

How does INF-y affect MHC expression?

It enhances the expression of class I and II MHC molecules and Fc receptors.

What role do T regulatory cells (Tregs) play in the immune system?

They help establish peripheral tolerance to self-antigens and harmless antigens.

What cytokines are associated with Th17 cells?

The IL-17 family of cytokines, which are pro-inflammatory.

What is the role of IL-12 in T cell differentiation?

It promotes the differentiation of T cells into Th1 subsets.

What is the function of interleukin-3 (IL-3)?

It stimulates the proliferation of immature marrow cells not yet committed to a specific lineage.

What are the primary mediators of hematopoiesis?

Colony Stimulating Factors (CSF).

What is the function of granulocyte-macrophage colony stimulating factor (GM-CSF)?

It stimulates the production of granulocytes and macrophages.

What is the role of erythropoietin in the body?

It stimulates the production of red blood cells.

What is the effect of interleukin-10 (IL-10) on the immune response?

It has inhibitory effects, reducing pro-inflammatory cytokine production.

How does IL-4 influence B cell activity?

It promotes the activation and differentiation of B cells, leading to antibody production.

What is the significance of CD25 in T regulatory cells?

CD25 is the IL-2 receptor alpha subunit, important for Treg identification.

What is the relationship between IL-17 and rheumatoid arthritis (RA)?

IL-17 can perpetuate the inflammatory process in RA by inducing pro-inflammatory mediators.

What are the clinical uses of hematopoietic cytokines?

They are used to promote recovery of leukocyte and platelet production after chemotherapy.

What is the role of IL-7 in the immune system?

It is important for the development and survival of lymphocytes.

What is the function of thrombopoietin?

It stimulates the production of platelets.

How does Epstein-Barr virus evade the immune response?

It contains a gene that codes for a protein similar to IL-10, allowing it to escape destruction.

What is the effect of IL-17 on epithelial and endothelial cells?

It induces the expression of TNF-a, IL-1B, and IL-6.

What is a key characteristic of Th1 cells?

They primarily produce interferon-gamma (INF-y) and are important for cell-mediated immunity.

What is the function of lymphokine-activated killer (LAK) cells?

They enhance the cytotoxicity of NK cells against resistant targets.

What is the significance of FoxP3 in T regulatory cells?

FoxP3 is a transcription factor that is crucial for the development and function of Tregs.

What is the role of macrophage colony stimulating factor (M-CSF)?

It stimulates the production of macrophages and monocytes.

What is the primary role of interleukin-6 (IL-6) in the immune response?

It acts as a pro-inflammatory cytokine and is involved in the acute phase response.