Immunopathology - Week 7 - Immune disorders Flashcards
Explain the concept of autoimmunity.
Autoimmunity is a form of immunopathology. It is the body’s own immune system targets cells and tissues, a specific
organ, or may be far more widespread of the body.
Tolerance commencing in the embryo, occurring in the primary
lymphoid organ is called?
Central tolerance.
Tolerance continuing after birth in the secondary lymphoid organs is called?
Peripheral tolerance
In autoimmunity, what does self - tolerance do?
Self-reactive immune cells are killed in the lymphoid organs or
suppressed by regulatory T cells.
Explain how genetic and environmental factors relate to the development of autoimmune diseases.
Certain genes can make an individual more susceptible to autoimmune diseases. These genes regulate the immune system. For example, the human leukocyte antigen (HLA) genes are key players. Variants in these genes can affect how the immune system recognises the body’s own cells and the invaders. This can lead to the body attacking itself, causing an autoimmune disease.
Genes alone aren’t usually enough to trigger an autoimmune disease. Environmental factors often set the process in motion. Infections, diet and stress can all contribute to acquiring an auto immune disease.
Explain the Cross reacting antigens theory in the breakdown of tolerance.
A foreign antigen may closely resemble a self-Ag, so the immune response react with the self-Ag, resulting in an autoimmune disease.
E.g rheumatic fever (there is a sharing of antigens between the streptococcal cell wall and heart muscle)
Explain the Altered ratio of T helper to regulatory T cell populations theory in the breakdown of tolerance.
Interferes with the functions of the regulatory cells, which are to dampen the immune response -> the immune system becomes more active.
Explain the modified self-antigens theory in the breakdown of tolerance.
Injured tissue may result in an alteration of the self-Ag, and hence viewed as ‘foreign’ ->
initiated immune response.
Explain the Sequestered antigens theory in the breakdown of tolerance.
- Some tissues are ‘hidden’ from the immune system e.g
blood-brain and blood-eye barriers. - Self-antigens are thus never exposed to the immune
system and do not go through the normal process of self-tolerance. - If that barrier fails -> the previously sequestered cells are
exposed to the immune system and can now be damaged.
Explain the Re-emergence of a ‘forbidden clone of
lymphocytes theory in the breakdown of tolerance.
In the process of developing self-tolerance, lymphocytes which could react with the person’s tissues are normally destroyed.
Occasionally, one of these may survive, and years later re-emerge and start to damage tissue.
What is the concept of alloimmunity?
Alloimmunity refers to the reaction of the
immune system to cells or tissues of
another individual from the same
species.
Examples:
* Transfusion reactions, incompatibility
between the donor and recipient blood
* Transplant rejections, incompatibility
between the HLAs of donor and recipient.
Name some examples of autoimmune diseases?
- Rheumatoid arthritis
- Systemic Lupus Erythematosus (SLE)
- Type 1 Diabetes
- Graves disease
- Inflammatory bowel disease
- Multiple sclerosis
Name some examples of alloimmune diseases?
- Transfusion rejection
- Transplant rejection
What is the aetiology of Rheumatiod arthritis?
Unknown
- Leads to autoimmune reaction that affects both articular and extra-articular tissues.
What is the pathogenesis of Rheumatiod arthritis?
The synovial membrane is thickened by chronic
inflammatory changes.
What is the epidemiology of Rheumatiod arthritis?
- Women are affected approximately 3
times as often as men. - First degree relatives have a 2-3 X
higher risk. - Peak age of onset: 35-50 years.
- May occur in children.
What is the clinical manifestations of Rheumatiod arthritis?
- Arthralgia (joint pain)
- Myalgia (muscle pain)
- Joints turn painful and swollen
- Restricted joint movements
- Subluxation of joints
What is the aetiology of Systemic lupus erythematosus?
The aetiology of SLE is unknown, but it appears to be multifactorial, including a generic predisposition and
environmental factors.
What is the pathogenesis of Systemic lupus erythematosus?
The predominant lesion is a vasculitis of arterioles,
capillaries and venules, associated with fibrinoid necrosis and inflammatory cellular infiltrate.
What is the epidemiology of Systemic lupus erythematosus?
- Females : Males (9:1).
- A peak incidence occurs between the
ages of 12 and 40. - Most commonly presents in the 20-30
year age group.
What is the clinical manifestations of Systemic lupus erythematosus?
- Fever, rash, joint pain
- Ulcers
- Seizures
- Psychosis
Explain the ABO system in blood typing.
The ABO system, blood types are described as O, A, B and AB.
* Type A blood, has Antigen A on the surface of the RBCs, and antibodies to
the B antigen in their plasma.
* Type B blood, has Antigen B on the surface RBCs, and antibodies to the A
antigen in their plasma.
* Type AB blood, has Antigens A & B on the surface of the RBCs, and no
antibodies to A or B antigens in their plasma.
* Type O blood, has neither A nor B antigen on the surface of the RBCs, and has antibodies to both A and B antigen in their plasma.
Explain the Rh system in blood typing.
The Rh system is a way of classifying blood based on whether or not you have a special protein (called the D antigen) on your red blood cells.
If you have the D antigen → you are Rh-positive.
If you don’t have the D antigen → you are Rh-negative.
