Lecture 8 Cytokines

A set of flashcards based on lecture notes covering the functions, types, and mechanisms of cytokines within the immune system.

What are cytokines?

Small proteins used by cells to communicate with one another in the immune system.

How many cytokines are present in humans?

Nearly 50 cytokines and about 40 chemokines.

What role do cytokine receptors play?

Cytokine receptors on target cells interact with cytokines to initiate downstream signaling pathways.

What are the three types of actions that cytokines can have?

Endocrine, paracrine, and autocrine actions.

What is pleiotropy in terms of cytokine action?

The ability of one cytokine to have different effects on different cell types.

What is redundancy in cytokine function?

The existence of multiple cytokines that can perform similar functions.

Define synergy in the context of cytokines.

When the combined effect of two or more cytokines is greater than the sum of their individual effects.

What does antagonism mean in cytokine signaling?

When one cytokine inhibits the action of another cytokine.

What is cascade induction regarding cytokines?

The process by which the action of one cytokine induces the production of additional cytokines.

Give an example of pleiotropy using interleukin-4.

Interleukin-4 can cause B cells to produce antibodies, T cells to proliferate, and mast cells to mediate allergic responses.

What is an example of redundancy in cytokines?

Multiple pro-inflammatory cytokines (like IL-1, IL-6, and TNF-alpha) can promote similar inflammatory responses.

How does interleukin-2 function as a T cell growth factor?

It supports the proliferation and differentiation of T cells, particularly CD4+ T cells.

What is the primary source of interleukin-1?

Produced mainly by macrophages as a pro-inflammatory cytokine.

How does interleukin-6 contribute to fever?

It acts on the hypothalamus to increase body temperature as part of the immune response.

What role does tumor necrosis factor (TNF) alpha play in inflammation?

It is a pro-inflammatory cytokine that can induce shock at high concentrations.

Describe interleukin-10's function.

An anti-inflammatory cytokine that inhibits immune responses.

What are the two forms of TNF alpha?

Transmembrane and soluble forms.

What is the significance of common chains in cytokine receptors?

Common chains may lead to a single failure affecting multiple cytokine functions.

What distinguishes interleukin-2 receptors upon T cell activation?

They express an additional third chain that increases affinity for IL-2.

What is the JAK-STAT signaling pathway?

A pathway where cytokines activate JAK kinases, leading to phosphorylation of STAT proteins that regulate gene expression.

What do chemokines primarily do?

They induce chemotaxis, directing immune cells to sites of infection.

What is an endogenous pyrogen?

A cytokine produced by human cells that can induce fever.

How do cytokines maintain homeostasis in the immune system?

By regulating immune cell distribution and function even in absence of infection.

How can antibody therapy be used clinically in relation to cytokines?

Antibodies may neutralize specific cytokines to mitigate inflammatory diseases.

What is the role of interleukin-15 in the immune response?

It is crucial for the survival and maintenance of memory T cells.

What stimulates the production of acute phase proteins during an infection?

Interleukin-6 stimulates the liver to produce these proteins.

Why is the study of cytokines important in immunology?

Cytokines are essential for proper immune system functioning and responses to infection.

What is a mitogen?

A substance that stimulates cell division, promoting cytokine production.

What determines the action of a cytokine on target cells?

The presence of specific receptors on the target cells.

What effect do cytokines have when there is an infection present?

Cytokine levels increase to initiate and enhance immune responses.

Which cytokine recruits neutrophils to an infection site? What are the underlying mechanisms of IL-8 recruiting neutrophils?

IL-8 is a cytokine that recruits neutrophils to an infection site.

1. Chemotaxis: IL-8 acts as a chemokine that attracts neutrophils by binding to specific receptors (CXCR1 and CXCR2) on their surface. This leads to migration of neutrophils towards the higher concentration of IL-8 at the site of infection.

2. Activation: Binding of IL-8 to its receptors activates neutrophils, enhancing their ability to respond to pathogens through increased phagocytosis, degranulation, and the production of reactive oxygen species.

3. Adhesion: IL-8 upregulates integrins on neutrophils, increasing their adhesion to endothelial cells and facilitating their passage through blood vessel walls to the site of inflammation.

What are the key elements of JAK-STAT signalling pathway and their functions?

1. Janus Kinases (JAKs)

   • Function: They are a family of cytoplasmic tyrosine kinases that associate with cytokine receptors and are activated upon cytokine binding.

2. Signal Transducers and Activators of Transcription (STATs)

   • Function: They are transcription factors that are phosphorylated by JAKs, allowing them to dimerize and translocate to the nucleus to regulate gene expression.

3. Cytokine Receptors

   • Function: They bind to specific cytokines and initiate the activation of JAKs upon cytokine binding.

The JAK-STAT pathway plays a crucial role in mediating effects of various cytokines, including those involved in immune responses.

Which cytokine inhibits inflammatory response?

IL-10 inhibits inflammatory responses by suppressing the expression of pro-inflammatory cytokines and promoting the development of regulatory T cells.

Which cytokine induces the production of acute phase proteins?

IL-6 induces the production of acute phase proteins, which are part of the body's response to inflammation.

IL-2 plays an important role in T cell activation by antigen. Why?

IL-2 is crucial for T cell activation because it stimulates the proliferation and differentiation of T cells after they recognize an antigen. It helps enhance the immune response by promoting the growth of T cells that have captured the specific antigen.

Which cytokines induce fever?

Cytokines that induce fever include IL-1, IL-6, and TNF-alpha.

What is the primary function of IL-1?

The primary function of IL-1 (Interleukin 1) is to mediate inflammatory responses. It plays a crucial role in the immune system by promoting the activation of lymphocytes, inducing fever, and stimulating the production of other inflammatory cytokines.