Autoimmunity Flashcards
(33 cards)
What is autoimmunity
Failure of organism to recognise its own constituent part as non-self
What are factors involved in developing autoimmune disease
Genetics - HLA
Hormonal - W>M
Environment
Immune regulation
Examples of environment
UV sun = apoptosis in SLE exposing T cell to ANA Ab which as seen as foreign
Infection = breakdown in tolerance
Chemicals / drugs
What are the pathogenetic mechanisms of different autoimmune disease
Cell mediated
Ab mediated
Immune complex mediated
Mixed / atypical
What happens in Cell mediated
Breakdown in immune tolerance
T cell bypass
T / B cell discordance
What is T cell bypass
B cells usually activated by alerted T cells
Can be bypassed by polyclonal activation of B cells e.g. super antigens in infection
What is T / B cell discordance
T and B cells should respond to same antigen
If they don’t B cells use ANY T cell stimulated by antigen to do the work
What diseases are cell-mediated autoimmune
DM
Chron’s
Psoriasis
Coeliac
What happens in DM
Autoreactive T cells against pancreatic islet cell antigen = destruction
What happens in Chron’s
Foreign pathogen in gut = APC to CD4
Autoreactive T cells attack
Inflammation
What gene associated
NOD2
What happens in Psoriasis
Autoreactive T cells attack skin associated antigens leading to inflammation and thickening
What happens in coeliac
B cells for transglutmainase (anti-TTG Ab) helped by T cells to recognise gliadin (concordance)
APC picks up gladden and presents to T cell
Recognise as foreign and attacks
If can’t find gliaden attacks other cells in gut
What happens in Ab mediated
Ab binds to self antigen due to failure of B cell
Leads to damage by Fc receptor MO +- complement
What is it an example of
Type 2 hypersensitivity reaction
What diseases are Ab autoimmune mediated
Anti-GBM Autoimmune anaemia ITP Myasthenia Gravis Pemphigus Hyperactive graft rejection Haemolytic disease newborn
What happens in Good pasture
IgG Ab reacts to type 4 collagen Activates complement Type 4 collagen destroyed in BM Pulmonary haemorrhage if in lung Renal failure if kidney
What increases risk inc HLA
HLA DR15
Infection
Smoking
Solvents
What is Myasthenia Gravis
Autoreactive T and B cells produce ACH Ab that block or destroy Ach receptor at NMJ preventing nerve impulses
Complement = local inflammation
What is present in majority of Myasthenia gravis
Ach receptor Ab
What happens in immune complex mediated autoimmunity
Immune complex forms
Activates phagocytes and causes damage
What is it an example of
Type 3 hypersensitiity
What disease associated
SLE
What happens in SLE
Failure of tolerance = self reactive B an T cells circulate
React to double stranded DNA auto-antigen
Present to B cell + T cell
Ab produced
Antigen / Ab complex made which is deposited in basement membrane
Activates complement
