Cytokines Chapter 3

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What is the primary function of IL-2 in terms of cytokine-receptor interactions?

T-cell activation

What is a characteristic of cytokines in terms of their production?

They require a stimulus for production

Which type of cytokine binding results in the activation of cells in the immediate vicinity?

Paracrine binding

Which of the following cytokine families includes IL-2 and IL-4?

Hematopoietin family

What is the primary source of cytokines?

TH cells and macrophages

What is a function of cytokines secreted by TH cells?

Activation of B cells, CTLs, MΦ, and NK cells

What is the primary characteristic of acute phase of inflammation?

Accumulation of fluid and leukocytes

Which type of cytokine promotes systemic inflammation?

Proinflammatory cytokine

What is the primary function of anti-inflammatory cytokines?

To reduce inflammation and promote healing

What is the role of cytokines in host responses?

To regulate host responses to infection, immune responses, inflammation, and trauma

What is the effect of proinflammatory cytokines on disease?

They make disease worse

What is the primary difference between proinflammatory and anti-inflammatory cytokines?

Proinflammatory cytokines promote inflammation, while anti-inflammatory cytokines reduce it

What is a common feature among the receptors for IL-2, IL-4, and IL-7?

They share a common γ chain

What is the consequence of cytokine binding to its receptor?

Aggregation of the receptors at the cell surface

What type of immunity is activated by Th1 cells?

Cell-mediated immunity

Which of the following cytokines is not typically produced by Th2 cells?

IL-2

What is the primary target of the cytokine IL-7?

Stem cells

What type of cytokine is IL-10?

Th2 cytokine

What is the role of JAKs in cytokine signaling?

To phosphorylate STATs and themselves

What is the effect of bacterial cell wall endotoxins on macrophages?

They stimulate macrophages to produce IL-1 and TNF-α.

What is the role of Th2 cells in immune responses?

Activate B cells

Which cytokine is a chemokine that primarily targets neutrophils and endothelial cells?

IL-8

What is the consequence of a defective γ chain in X-linked severe combined immunodeficiency disease (SCID)?

Impaired cytokine signaling

What type of bacteria can cause bacterial septic shock?

Gram-negative bacteria.

What is the result of phosphorylation of STATs by JAKs?

Dimerized STATs translocate to the nucleus

What is a common symptom of bacterial septic shock?

A drop in blood pressure.

What is the primary mechanism by which bacterial septic shock develops?

Bacterial cell wall endotoxins stimulate macrophages to overproduce IL-1 and TNF-α.

What is one of the roles of cytokines in immune responses?

To initiate inflammation

What is a potential therapeutic strategy for treating bacterial septic shock?

Using antagonists to block the effects of IL-1 and TNF-α.

Study Notes

Cytokines

  • Cytokines are soluble messenger molecules, which are low molecular weight proteins secreted by various cells, playing a crucial role in the induction and regulation of immune responses.
  • They can activate many cells, but their production requires a stimulus, and they bind to specific receptors with high affinity, inducing gene activation.

Cytokine Receptor Interactions

  • Cytokines can bind receptors and alter gene expression.
  • There are three primary functions of cytokine-receptor interactions:
    • Autocrine: affects the secreting cell (self).
    • Paracrine: affects cells in the immediate vicinity, binding another cell close by.
    • Endocrine: affects cells remote from the secreting cell.

Categories of Cytokines

  • There are four structural families of cytokines:
    • Hematopoietin family (IL-2, IL-4).
    • Interferon family.
    • Chemokine family.
    • Tumor Necrosis Factor (TNF) Family.

Cells That Make Cytokines

  • A variety of cells can produce cytokines, but the primary sources are T helper (TH) cells and macrophages (MΦ).
  • Cytokines secreted by TH cells can affect B cells, cytotoxic T cells (CTLs), MΦ, and natural killer (NK) cells.
  • Cytokines are involved in hematopoiesis, adaptive immunity, innate immunity, and inflammation.

Inflammation and Cytokines

  • Inflammation is characterized by increased blood flow and vascular permeability, along with the accumulation of fluid, leukocytes, and inflammatory mediators like cytokines.
  • Inflammatory cytokines can be divided into two groups:
    • Those involved in acute inflammation.
    • Those responsible for chronic inflammation.
  • Proinflammatory cytokines promote systemic inflammation, while anti-inflammatory cytokines reduce inflammation and promote healing.

Functions of Cytokines

  • Various cytokines have different functions, including:
    • IL-2: activates T cells and macrophages.
    • IL-4: involved in hematopoiesis and activates TH2 cells and B cells.
    • IL-6: induces acute-phase proteins and activates TH2 cells and B cells.
    • IL-7: involved in hematopoiesis.
    • IFN-γ: activates macrophages and induces the production of reactive oxygen species.

CD4+ T Helper Subsets

  • CD4+ T helper cells can be divided into subsets based on their cytokine production:
    • TH1 cells produce IL-2, IFN-γ, and TNF-β, activating cell-mediated immunity.
    • TH2 cells produce IL-4, IL-6, and IL-10, activating humoral immunity.

Receptor Signaling

  • Most cytokine receptors are not expressed in high numbers in completely resting cells but are upregulated after cell activation.
  • Ligand binding causes the aggregation of receptors at the cell surface, leading to the phosphorylation of JAKs and STATs, and eventually, gene expression.

Roles of Cytokines in Immune Responses

  • Cytokines play key roles in:
    • Initiating inflammation.
    • T-cell priming.
    • The development of T-cell specialization.
    • The winding down of the immune response.

Understand the functions of cytokines, including their binding to receptors, altering gene expression, and three primary functions. Learn about autocrine, paracrine, and endocrine interactions, and their role in T-cell activation and inflammation.

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