Allergic Reactions and Immune Responses

Questions and Answers

Which of the following symptoms is NOT commonly associated with acute systemic immune responses to drugs?

Wheezing or breathing problems

Skin rash or hives

Anaphylaxis

Nausea and vomiting (correct)

What is the typical timing for an acute allergic reaction to drugs following exposure?

24 to 72 hours

5 to 8 hours

30 minutes to 2 hours

2 to 30 minutes (correct)

Which of the following drugs is commonly implicated in triggering allergic reactions?

Acetaminophen

Calcium supplements

Penicillin (correct)

Vitamin C

Chronic stimulation or impairment of immune cells can lead to which type of hypersensitivity reaction?

Type IV hypersensitivity Signup and view all the answers

What role do NK cells play in the immune response related to antibody-dependent cellular cytotoxicity (ADCC)?

They mediate cell damage in partnership with antibodies. Signup and view all the answers

What is the primary mechanism of allergen recognition in Type I hypersensitivity reactions?

Binding of IgE to allergen à cross-linking on mast cell surface Signup and view all the answers

Which of the following is a characteristic of Type IV hypersensitivity reactions?

Activation of CD4+ T cells à cytokine release Signup and view all the answers

What is the role of IL-4 in allergic immune activation?

Activation of B cells à IgE production Signup and view all the answers

Which of the following is a symptom of anaphylaxis?

Release of histamine à increased vascular permeability Signup and view all the answers

What is the primary function of IgE in allergic reactions?

Binding to allergen à cross-linking on mast cell surface Signup and view all the answers

Study Notes

Allergens and Immune Response

Food allergens include wheat and dairy products; inhaled allergens include house dust mites and pollens.
Medications like penicillin can also induce allergic responses.
Immune responses depend on the exposure route (skin, injection, ingestion, inhalation) and immune response type.

Allergic Immune Activation

Allergen exposure triggers cytokine release (e.g., IL-25, IL-33, TSLP) leading to:
- Activation of ILC2s and local antigen-presenting cells (APCs).
- T cell activation results in Th2 cell differentiation in the presence of IL-4.
- B cell activation produces IgE under IL-4 influence.
- Mast cells activated by IgE lead to histamine release.
- Eosinophils are activated by IL-5.

Responses in Pre-sensitized Individuals

Immediate response caused by mast cell activation and release of granular molecules.
Late-phase response includes:
- Activation of APC and Th2 cells.
- T cell proliferation and eosinophil activation.

Hypersensitivity Reactions (Type I-IV)

Type I (IgE-mediated): IgE antibodies bound to allergens cause mast cell degranulation.
Type II (Antibody-mediated): IgG/IgM antibodies target cell-associated antigens, resulting in complement activation.
Type III (Immune complex): Formation of immune complexes leads to tissue damage through complement activation.
Type IV (Cell-mediated): Involves Th1 and CTL responses against soluble and cell-associated antigens.

Comparison of Hypersensitivity Types

Type I: Fast (2-30 mins), e.g., allergic rhinitis, systemic anaphylaxis.
Type II: Medium response (5-8 hours), involves drug allergies, and blood transfusion reactions.
Type III: Moderate (2-8 hours), e.g., serum sickness and arthus reaction.
Type IV: Slow onset (24-72 hours), e.g., graft rejection, allergic contact dermatitis.

Systemic Immune Responses to Drugs

Sensitization can delay initial responses but triggers rapid reactions on subsequent exposures.
Symptoms include skin rashes, itching, breathing difficulties, joint pains, and potentially life-threatening anaphylaxis.
Common triggers: penicillin, sulfonamide antibiotics, NSAIDs, anticonvulsants, chemotherapy drugs.

Mechanisms of Drug-Induced Allergies

Direct Presentation/Non-hapten: Drug alters MHC peptide complex leading to T cell activation.
Hapten Mechanism: Drugs bind to carrier proteins, rendering them immunogenic; pro-haptens become reactive metabolites.

Adaptive Immune Response

The immune system responds to drugs as pathogens, activated via all four hypersensitivity types.
Drug type and immune context influence the activated response.

Diagnosis and Management

Skin tests can confirm allergic responses; drug challenges may be performed cautiously.
Management strategies include drug avoidance, antihistamines, bronchodilators, adrenaline, and desensitization.

Key Cytokines in Allergic Response

T and B cell activation leads to antibody production; cytokines dictate antibody isotype switching.
IL-4 promotes IgE synthesis, characteristic of Type I hypersensitivity.

Description

This quiz covers various types of allergens, including food, inhaled allergens, and medications. It also discusses how the route of exposure influences the immune response and the sites where exposure occurs, such as skin, injection, ingestion, and inhalation.