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Related Concept Videos

Hypersensitivities01:30

Hypersensitivities

Hypersensitivity, also known as a hypersensitivity reaction or allergic reaction, is a condition where the body's immune system reacts abnormally to a foreign substance. Such substances, that cause hypersensitivity are referred to as an allergen, could be something typically harmless to most people, like pollen or certain foods.
Types of Hypersensitivities
Hypersensitivity reactions are categorized into four types: Type 1, Type 2, Type 3, and Type 4. Each type has a distinct mechanism...
Hypersensitivity Reactions: Immune-Complex Reactions01:19

Hypersensitivity Reactions: Immune-Complex Reactions

Type III hypersensitivity reactions occur when antigen–antibody complexes form and activate the complement system. Normally, these complexes help the clearance of antigens by phagocytes and red blood cells. However, when large numbers of immune complexes are present, they can deposit in tissues—particularly in the walls of blood vessels—leading to inflammation and tissue injury. These deposits trigger complement activation and neutrophil recruitment, resulting in serum sickness, a systemic...
Hypersensitivity Reactions: Delayed Hypersensitivity Reactions01:29

Hypersensitivity Reactions: Delayed Hypersensitivity Reactions

Delayed-Type Hypersensitivity (DTH), or Type IV hypersensitivity, is a cell-mediated immune response. It occurs when T cells, rather than antibodies, mediate a reaction to specific antigens. It is characterized by a delayed onset (1-2 days) and involves the recruitment of macrophages to the inflammation site.The initiation of a DTH response begins with the sensitization of T cells. During this phase, which lasts at least 1-2 weeks, antigen-specific T cells are activated, clonally expanded, and...
Drug Toxicity: Allergic Reactions01:30

Drug Toxicity: Allergic Reactions

Drug-related allergies are immune-mediated responses triggered by the administration of pharmacological agents. These hypersensitivity reactions are classified based on the immune mechanisms involved. The four primary types—Type I, II, III, and IV—are mediated by different immunological pathways and exhibit distinct clinical manifestations.Type I Hypersensitivity/ IgE-Mediated Reactions: Immunoglobulin E (IgE) immediately mediates Type I hypersensitivity reactions. Upon initial exposure to a...
Pneumonia I: Introduction01:29

Pneumonia I: Introduction

Pneumonia is an infection of the lower respiratory tract that leads to inflammation of the lung parenchyma, often resulting in the accumulation of inflammatory exudate in the alveoli and airways. Unlike the watery, low-protein fluid exudate in pulmonary edema, the exudate in this case is a thick fluid rich in immune cells, proteins, and debris produced during infection and inflammation.This impairs gas exchange and can lead to consolidation of lung tissue. The infection may be caused by a...
Pneumonia I: Introduction01:30

Pneumonia I: Introduction

Pneumonia is an acute respiratory infection that targets the lungs, specifically the alveoli. These tiny air sacs, essential for oxygen exchange, become engorged with pus and fluid, severely hindering breathing, decreasing oxygen absorption, and causing significant pain and discomfort during respiration.
Risk Factors
Various factors influence the likelihood of developing pneumonia. Age plays a crucial role, with infants, children under two, and individuals over 65 at increased risk due to their...

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Experimental Model to Evaluate Resolution of Pneumonia
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Hypersensitivity pneumonitis.

Shinichiro Ohshimo1, Francesco Bonella, Josune Guzman

  • 1Department of Molecular and Internal Medicine, Graduate School of Biomedical Sciences, Hiroshima University, Japan.

Immunology and Allergy Clinics of North America
|October 30, 2012
PubMed
Summary
This summary is machine-generated.

Hypersensitivity pneumonitis can mimic other lung diseases, making diagnosis challenging. Identifying the specific antigen is not always possible, highlighting the need for thorough environmental history in diagnosing interstitial lung disease.

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The Utilization of Oropharyngeal Intratracheal PAMP Administration and Bronchoalveolar Lavage to Evaluate the Host Immune Response in Mice
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Last Updated: May 17, 2026

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12:27

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Published on: April 2, 2014

Area of Science:

  • Pulmonology
  • Immunology
  • Radiology

Background:

  • Hypersensitivity pneumonitis (HP) presents with varied clinical features, often resembling other interstitial lung diseases (ILDs).
  • The onset of HP is typically gradual and insidious, complicating early recognition.
  • Accurate diagnosis of HP is crucial for effective management and preventing irreversible lung damage.

Purpose of the Study:

  • To emphasize the diagnostic challenges posed by hypersensitivity pneumonitis.
  • To highlight key diagnostic modalities for identifying HP.
  • To underscore the importance of considering HP in all ILD cases and the necessity of environmental exposure assessment.

Main Methods:

  • Review of clinical manifestations and diagnostic approaches for hypersensitivity pneumonitis.
  • Analysis of the utility of high-resolution computed tomography (HRCT) and bronchoalveolar lavage (BAL) in HP diagnosis.
  • Evaluation of the frequency of unidentified causative antigens in HP patients.

Main Results:

  • Clinical symptoms of HP frequently overlap with other interstitial lung diseases.
  • High-resolution computed tomography and bronchoalveolar lavage are sensitive and characteristic diagnostic tools for HP.
  • In 20-30% of patients, the specific antigen responsible for hypersensitivity pneumonitis remains unidentified.

Conclusions:

  • Hypersensitivity pneumonitis should be a primary consideration in the differential diagnosis of all interstitial lung diseases.
  • A comprehensive environmental exposure history is mandatory for diagnosing HP.
  • Clinicians must maintain a high index of suspicion for HP, even when antigen identification is not feasible.