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Antigens Involved in Adaptive Immunity

Antigens Involved in Adaptive Immunity

An antigen is any substance the immune system identifies as foreign and potentially harmful to the body, prompting an immune response. Antigens have two functional properties: immunogenicity and reactivity. Immunogenicity is the ability of an antigen to stimulate a specific immune response. At the same time, reactivity describes the antigen's ability to react with the cells and antibodies produced in response to it.
Complete Antigens
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Hypersensitivity Reactions: Cytolytic Reactions

Hypersensitivity Reactions: Cytolytic Reactions

Type II hypersensitivity involves IgG and IgM antibodies targeting cell surface antigens, leading to cell destruction. This can occur through complement activation, antibody-dependent cell-mediated cytotoxicity (ADCC), or acting as opsonins for phagocytosis. When excessive, these reactions cause significant tissue damage.Drug-induced hemolytic anemia is a common example, where drugs like penicillin or cephalosporins bind to red blood cells, forming drug-protein complexes. These complexes...

Hemoglobin

Hemoglobin

Hemoglobin is a globular protein made up of four subunits. Two of these subunits are alpha chains, and the other two are beta chains. Each subunit contains a molecule of heme, which has an iron atom and can bind to oxygen. When an oxygen molecule binds to one heme group, it changes the shape of hemoglobin, making it easier for the other heme groups to bind oxygen as well.
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Antibody Actions

Antibody Actions

Antibodies, or immunoglobulins, are critical players in the immune system's arsenal against invading pathogens. Produced by B cells and plasma cells, their primary role is to detect and bind to specific antigens, molecules found on the surface of pathogens like bacteria or viruses. Beyond antigen recognition, antibodies perform several vital functions that contribute to immune defense.
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Antigen Processing Pathways

MHC molecules are key players in the immune response, enabling T cells to recognize and respond to specific antigens. They are present on the surface of all nucleated cells in the body and are instrumental in presenting antigens to T cells and activating them. T cells recognize the MHC-antigen complex and initiate an immune response. MHC class I and MHC class II are two main types of MHC molecules, each associated with a distinct antigen processing pathway.
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Related Experiment Video

Updated: Apr 1, 2026

Measurement of Heme Synthesis Levels in Mammalian Cells

Measurement of Heme Synthesis Levels in Mammalian Cells

Published on: July 9, 2015

Heme as a danger molecule in pathogen recognition.

Barbara Wegiel¹, Carl J Hauser¹, Leo E Otterbein¹

¹Department of Surgery, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215.

Free Radical Biology & Medicine

|October 13, 2015

Summary

Redox control is vital for innate immunity, with danger signals (PAMPs and DAMPs) activating the HO-1 gene. This process enhances immune response and host survival through a two-hit cycle involving carbon monoxide signaling.

Keywords:

ATP Carbon monoxide (CO)Danger associated molecular patterns (DAMPs)Heme Heme oxygenase-1 Inflammasome Reactive oxygen species (ROS)

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Last Updated: Apr 1, 2026

Measurement of Heme Synthesis Levels in Mammalian Cells

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Published on: July 9, 2015

Staphylococcus aureus Growth using Human Hemoglobin as an Iron Source

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Published on: February 7, 2013

Using a Bacterial Pathogen to Probe for Cellular and Organismic-level Host Responses

Using a Bacterial Pathogen to Probe for Cellular and Organismic-level Host Responses

Published on: February 22, 2019

Area of Science:

Immunology
Redox Biology
Molecular Biology

Background:

Innate immune responses rely on precise redox control.
Pathogen-associated molecular patterns (PAMPs) and danger-associated molecular patterns (DAMPs) signal danger to the host.
These signals activate stress response pathways, including the heme oxygenase-1 (HO-1) gene.

Purpose of the Study:

To review the role of the stress response gene heme oxygenase-1 (HO-1) in innate immunity.
To explore how PAMPs and DAMPs activate HO-1 and its therapeutic potential.
To elucidate the communication between host and bacteria mediated by HO-1 and its products.

Main Methods:

Literature review focusing on redox mechanisms in innate immunity.
Analysis of signaling pathways involving PAMPs, DAMPs, nrf2, and HO-1.
Discussion of the role of heme and carbon monoxide (CO) in immune activation.

Main Results:

Both PAMPs and DAMPs activate the redox-sensitive protein nrf2, leading to increased HO-1 expression.
Heme degradation by HO-1 produces carbon monoxide (CO), a signaling molecule.
Bacterial endotoxin activates HO-1, and generated CO enhances bacterial ATP production, amplifying the immune response.

Conclusions:

HO-1 is a critical regulator of the host's response to sterile and infectious stimuli.
A two-hit cycle involving CO signaling enhances leukocyte activation and bacterial clearance.
Understanding these host-microbe interactions offers therapeutic potential for inflammatory diseases.