Delayed-type hypersensitivity reactions in the skin a) are...

Name: Problem 5, Chapter 17: Nester's Microbiology: A Human Perspective
Uploaded: 2021-06-30T11:14:29-08:00
Duration: 1 min 23 s
Channel: Joanna Quigley
Description: Delayed-type hypersensitivity reactions in the skin a) are characterized by a wheal and flare reaction. b) peak at 4 to 6 hours after exposure to antigen. c) require complement activation. d) show induration because of the influx of sensitized T cells and macrophages. e) depend on activities of the Fc portion of antibodies.

Delayed-type hypersensitivity reactions in the skin a) are characterized by a wheal and flare reaction. b) peak at 4 to 6 hours after exposure to antigen. c) require complement activation. d) show induration because of the influx of sensitized T cells and macrophages. e) depend on activities of the Fc portion of antibodies.

Delayed-type hypersensitivity reactions in the skin
a) are characterized by a wheal and flare reaction.
b) peak at 4 to 6 hours after exposure to antigen.
c) require complement activation.
d) show induration because of the influx of sensitized T cells and macrophages.
e) depend on activities of the Fc portion of antibodies.

Key Concepts

Delayed-type Hypersensitivity

Delayed-type hypersensitivity (DTH) is a type of immune reaction that is primarily mediated by T lymphocytes rather than antibodies. It is characterized by a delayed response—typically 24 to 72 hours after exposure to the antigen—resulting in localized inflammation and tissue induration.

Cell-mediated Immune Response

A cell-mediated immune response involves the activation of T cells, which recognize specific antigens and release cytokines. These cytokines recruit and activate macrophages and other inflammatory cells, leading to the characteristic swelling and induration seen in delayed-type hypersensitivity reactions.

Induration in Skin Reactions

Induration refers to the hard, raised area observed on the skin during DTH reactions, resulting from the accumulation of activated T cells and macrophages. This feature differentiates DTH from immediate hypersensitivity reactions, which typically produce a wheal and flare pattern.

Distinction from Antibody-mediated Reactions

Delayed-type hypersensitivity is distinct from antibody-mediated (immediate) hypersensitivity responses. Unlike reactions that depend on the activation of complement or the Fc portion of antibodies—which are central to processes such as the wheal and flare reaction—DTH is entirely mediated by T cells and does not involve complement activation.

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