Hypersensitivity and Autoimmunity Flashcards
Define hypersensitivity
A group of disorders where the normally beneficial components of the immune response act in an exaggerated or inappropriate fashion to environmental antigens which do not normally cause tissue damage. The exaggerated response directed at the antigen rather than the antigen itself is responsible for the tissue damage which results (bystander damage).
Define atopy.
Atopy refers to the genetic tendency to develop allergic diseases such as allergic rhinitis, asthma and atopic dermatitis (eczema). Atopy is typically associated with heightened immune responses to common allergens, especially inhaled allergens and food allergens.
What is a hapten?
Haptens are small molecules that elicit an immune response only when attached to a large carrier such as a protein; the carrier may be one that also does not elicit an immune response by itself.
Describe the pathogenetic mechanisms involved in autoimmune disease
o Cell-mediated o Antibody-mediated o Antibody + Complement o Immune Complex-mediated o Recruitment of innate compounds
What sequence of events are thought to lead to the development of autoimmune disease?
o The initiating event (e.g. infection) plus some sort of genetic susceptibility leads to the breakdown of self tolerance
o This leads to the initiation of autoreactivity
o These autoreactive responses can either be humoral or cellular, and eventually lead to cell damage
Define tolerance
The process whereby the immune system avoids producing damaging reactions against self-antigens. Arises through deletion of autoreactive T and B cells during cell maturation (central tolerance) or by inhibiting the activity of autoreactive cells which escape the central tolerance process (peripheral tolerance).
What haps mediate peripheral tolerance?
o Treg cells o Antibody idiotype (Fab) regulation – regulatory Abs regulate effector Ab activity o Immune complex formation o Oral tolerance o Th17 cells
Describe the aetiology of autoimmune disorders
Multifactorial – interaction of
1) Genetic factors – familial predisposition
2) Immune regulatory factors – defective tolerance
3) Hormonal factors – particularly female hormones
4) Environmental factors – infectious agents, sunlight, drugs, nutritional factors
5) ‘Other’ factors – age, trauma, malignant disease
Give some examples of organ specific and non-organ specific autoimmune disorders
Organ Specific
• Thyroid - Hashimoto’s Thyroiditis, Primary Myxoedema, Thyrotoxicosis
• Stomach - Pernicious Anaemia
• Adrenal - Addison’s Disease
Non Organ Specific • Muscles - Dermatomyositis • Skin - Scleroderma • Kidneys - SLE • Joints - Rheumatoid Arthritis
