reaction to a bee sting

[pathologyguy]

A 5-year-old boy is brought to the emergency department for a severe reaction to a bee sting. His right hand and arm are very swollen and itchy. Which of the following substances is derived from mast cells and mediates this type of inflammatory response?

A. Bradykinin
B. C3a
C. C5a
D. Histamine
E. Leukotriene B4
F. Nitric oxide
G. Tumor necrosis factor

[Asclepius1]

Is it histamine?

[pathologyguy]

Originally Posted by pathologyguy

A 5-year-old boy is brought to the emergency department for a severe reaction to a bee sting. His right hand and arm are very swollen and itchy. Which of the following substances is derived from mast cells and mediates this type of inflammatory response?

A. Bradykinin
B. C3a
C. C5a
D. Histamine
E. Leukotriene B4
F. Nitric oxide
G. Tumor necrosis factor

Marvelous! Yes, Histamine...as in Mr. Histamine

The correct answer is D. Histamine is produced by mast cells as well as basophils and platelets. Mast cells release histamine in response to physical injury, heat, cold, type 1 hypersensitivity reaction, C3a and C5a anaphylatoxins, proteins released from leukocytes, substance P, and other stimuli. Histamine is the principal mediator of the immediate transient phase of increased permeability of venules in acute inflammation, an effect mediated by H1 histamine receptors.
Bradykinin (choice A) is a peptide of the kinin system, a group of circulating plasma proteins that generates vasoactive peptides by proteases called kallikreins. Similar to histamine, bradykinin mediates vascular leakage and pain.

C3a (choice B) and C5a (choice C) are complement components referred to as anaphylatoxins. These components increase vascular permeability by inducing the release of histamine. Hepatocytes and macrophages synthesize C3 and C5, respectively.

Neutrophils are the source of leukotriene B4 (choice E), which is a powerful chemotactic factor for neutrophils. It is synthesized via the lipoxygenase pathway of arachidonic acid metabolism.

Nitric oxide (choice F) is a short-lived mediator produced by endothelial cells, macrophages and specific neurons. NO elicits a number of biologic responses, including vasodilatation, inhibition of leukocyte rolling and adhesion, and inhibition of platelet aggregation. NO limits recruitment and activation of neutrophils in inflammation.

Tumor necrosis factor (choice G) is one of the major cytokines, which are proteins that modulate the function of certain cells by an autocrine, paracrine, or endocrine effect. TNF includes two different proteins. TNFα is secreted by activated macrophages and TNFβ is produced by activated T lymphocytes. TNFα and TNFβ mediate important actions in inflammation and induce (along with interleukin-1) the systemic acute-phase responses.