Hypersensitivities

This set of flashcards covers key concepts related to hypersensitivities, including types, mechanisms, examples, and treatments as discussed in the lecture.

What are hypersensitivities?

Hypersensitivities are immunological disorders characterized by abnormal responses to antigens.

What are the learning objectives of the lecture on hypersensitivities?

Outline different types of hypersensitivities, describe basic aetiology, explain examples, and describe treatments.

What factors contribute to immunological disorders?

Immunological disorders are multifactorial, involving a combination of genetic susceptibility and environmental factors.

What is the incidence of immune hypersensitivities between genders?

The incidence of immune hypersensitivities is twice as high in women compared to men.

What role do sex hormones play in hypersensitivities?

Sex hormones, particularly oestrogen, may influence the incidence and severity of hypersensitivities.

What types of hypersensitivities are discussed?

There are over 80 different hypersensitivities, including allergies and autoimmune diseases.

What is Type I hypersensitivity?

Type I hypersensitivity is an IgE-mediated response, often causing allergic reactions.

What are common examples of hypersensitivities?

Examples include Type 1 diabetes, rheumatoid arthritis, psoriasis, and multiple sclerosis.

Describe the Gell and Coombs classification.

Hypersensitivities are classified into four types: Type I (IgE-mediated), Type II (IgG-mediated), Type III (immune complex-mediated), and Type IV (cell-mediated).

What are the typical manifestations of Type I hypersensitivity?

Typical manifestations include anaphylaxis, hay fever, asthma, hives, food allergies, and eczema.

What is the mechanism of Type I hypersensitivity upon second exposure?

On second exposure, the allergen cross-links IgE on mast cells and basophils triggering degranulation.

What symptoms are caused by histamine in Type I hypersensitivity?

Histamine causes blood vessel dilation, increased permeability, mucus secretion, and smooth muscle contraction.

What are the treatments for Type I hypersensitivities?

Treatments include adrenaline injections for anaphylaxis, antihistamines, corticosteroids, and immunotherapy.

What is Type II hypersensitivity?

Type II hypersensitivity involves antibodies that bind to antigens on cell surfaces, leading to cell destruction.

Which disorders are examples of Type III hypersensitivity?

Examples include serum sickness, localized Arthus reactions, and systemic lupus erythematosus.

What characterizes Type IV hypersensitivity?

Type IV hypersensitivity is delayed and mediated primarily by T cells.

What role do T cells play in Type IV hypersensitivity?

T cells release cytokines that activate macrophages, mediating tissue damage.

What is allergic contact dermatitis?

Contact dermatitis is a local reaction mediated by T-lymphocytes initiating inflammation upon re-exposure to an antigen.

What are diagnostic tests for hypersensitivity?

Diagnostic tests include delayed cutaneous reactions (e.g., Mantoux Test) and in vitro tests for delayed hypersensitivity.

What are the two phases of Type IV hypersensitivity?

The two phases are sensitization phase and effector phase.

What are anti-inflammatory drugs used for?

They inhibit mediators of the inflammatory response, reducing pain and inflammation.

What is the purpose of immunosuppression in treatment?

To reduce immune system activation, but it also leaves the body vulnerable to infections.

What is Azathioprine used for?

Azathioprine inhibits purine synthesis and is used in lupus, Crohn's disease, and rheumatoid arthritis.

What are NSAIDs and how do they work?

Non-steroidal anti-inflammatory drugs inhibit cyclooxygenase enzymes to reduce inflammation and pain.

What is the function of cyclosporins?

Cyclosporins prevent T cell activation and are used post-transplant to prevent rejection.

What is the primary action of Etanercept?

A recombinant DNA drug that binds to TNF, preventing receptor binding and downregulating inflammation.

What is helminth therapy?

Helminth therapy involves using parasites to upregulate Th2 responses and reduce Th1 immune responses for autoimmune diseases.

What is an important consideration in treating hypersensitivities?

Treatments often focus on symptom management and inhibiting inflammation without compromising normal immune function.

What future direction is suggested for therapies targeting autoimmune diseases?

Future therapies aim to target specific hyper-responsive pathways in diseases.

What indicates a genetic component in Type I hypersensitivities?

Susceptibility to Type I hypersensitivities is inherited, affecting 20% to 30% of the population.

What factors can increase the risk of developing hypersensitivities?

Western diet, hygiene hypothesis, and lack of parasitic infections.

What is the role of immune complexes in Type III hypersensitivity?

Immune complexes can deposit in tissues, leading to inflammation and possible organ failure.

What is a common treatment method for contact dermatitis?

Topical treatments to reduce inflammation and allergic reactions caused by sensitization.

What is the main mechanism of action of corticosteroids?

Corticosteroids inhibit the production of inflammatory mediators and are used to control inflammation.

How are Type I hypersensitivities triggered in the body?

They are triggered by IgE antibodies reacting with specific allergens, causing an allergic reaction.

What is a challenge in the treatment of chronic hypersensitivity disorders?

The challenge lies in balancing effective treatment without suppressing normal immune function.

What systemic effects can generalized anaphylaxis cause?

Generalized anaphylaxis can lead to shock, extensive swelling, and dangerously low blood pressure.

What characterizes the immune response in Type IV hypersensitivity?

The immune response is characterized by a delayed reaction primarily mediated by T-helper cells.