What immune reactions caused by pathogens might trigger allergies, such as skin rashes or asthma?

Sourav PanNovember 11, 2024

Answered

The immune reactions triggered by pathogens can lead to allergies, manifesting as conditions such as skin rashes or asthma. Here’s how these immune responses work and their implications for allergic diseases:

Mechanisms of Allergic Reactions

1. Sensitization Phase:
   • Upon first exposure to an allergen (a normally harmless substance), the immune system may mistakenly identify it as a threat. This triggers the production of immunoglobulin E (IgE) antibodies specific to that allergen. These IgE antibodies bind to mast cells and basophils, which are types of white blood cells involved in allergic responses.
2. Subsequent Exposure:
   • On subsequent exposures to the same allergen, the allergen cross-links the IgE bound to mast cells and basophils, leading to their activation. This activation causes the release of various chemical mediators, including histamine, leukotrienes, and prostaglandins. These substances are responsible for the symptoms of allergic reactions, such as inflammation, itching, and mucus production .
3. Immediate vs. Late-Phase Reactions:
   • The initial response is often immediate, resulting in symptoms like sneezing, itching, or skin rashes (urticaria). This is followed by a late-phase response that can occur hours later, characterized by a more sustained inflammatory reaction involving additional immune cells like eosinophils and T helper type 2 (Th2) cells. This late-phase response can exacerbate conditions like asthma and lead to chronic symptoms.

Pathogen Interaction

1. Role of Pathogens:
   • Certain pathogens can influence the development of allergies by altering immune responses. For example, infections may skew the immune system towards a Th2-dominated response, which is associated with allergic conditions . This can happen when skin exposure to allergens occurs concurrently with infections, leading to heightened sensitization and subsequent allergic reactions.
2. Skin Exposure and Asthma:
   • Recent research indicates that skin may serve as a significant route for allergen exposure and sensitization, contributing to asthma development. Factors that impair skin barrier function can facilitate allergen entry, promoting Th2-like immune responses that can lead to asthma. For instance, individuals with atopic dermatitis (eczema) often have increased susceptibility to developing asthma due to compromised skin integrity allowing allergens to penetrate more easily.

Allergens and Symptoms

• Common allergens include pollen, dust mites, pet dander, and certain foods. When these allergens trigger an immune response, they can cause a range of symptoms:
  • Respiratory Symptoms: Such as nasal congestion and asthma attacks due to airway inflammation.
  • Dermatological Symptoms: Including rashes or eczema from localized allergic reactions on the skin .
• The connection between allergies and asthma is well established; many individuals with asthma also have allergic rhinitis or other allergic conditions