Autoimmunity Flashcards
What is autoimmunity?
Breakdown of tolerance to self-antigen - failure to regulate pathological immune responses
What causes autoimmunity?
Genetic Factors - genes coding for MHC, or other immune respnse genes such as those coding for TNF alpha and CTLA4
Hormonal Factors - such as SLE in females
Environmental Factors - infection, stress, diet etc
How does Type II hypersensitivity arise?
- Production of IgM, IgE to cell surface proteins or ECM proteins
- Autoantibody attak on target cell
- Autoantobody disruption of protein function
What is immune-mediated thrombocytopenia?
- Immunological attack on platlets causing defective clotting (prolonged bleeding, melaena, haematuria, epistaxis, petechial haemorrhages of skin and mucosal membranes)
- Diagnosed via reduced platlet count and anti-platlet antibodies found in serum
What is a pemphigius complex?
Autoantibodies to cellular adhesion molecules or ECM proteins of the basement membrane
causing vesicles, ulceration and crusting lesions of skin and mucocutaneous junctions
What are vesiculobullous lesions and how do they occur?
Disruption of stratified squamous epithelial cells by auto-antibodies targetting desmogleins disrupting cell-cell adhesion causing detachment of keratinocytes from each other
What is Type III hypersensitivity?
Antibody IgG binding to a soluble antigen causing immune complex disease
What occurs during Type III hypersensitivity?
- Depostition of Ag/Ab complexes in blood vessels
- Vasculitis
- anti-DNA/histone antibodies SLE = most common form
What are the two types of Type IV hypersensitivity?
CD4 T cell mediated (TH1: IFN-gamma): Abnormal activation of macrophages in healthy tissues, production of inflammatory mediators and MMp enzymes causes tissue damage
CG8 T cell mediated (CTL): CTLs kill healthy cells mistakenly thinking they are infected by a virus
