Lecture #14 Flashcards
What is hypersensitivity?
An antigenic response beyond what is considered normal (an allergy)
Type 1 hypersensitivity is called what type of response?
An anaphylactic response
During Type 1 hypersensitivity, what occurs during the first encounter with the allergen?
B cells differentiate into plasma and memory cells.
Memory cells make IgE which then binds to mast cells and basophils
What are the symptoms of the first encounter during hypersensitivity type 1
No apparent symptoms
Which type of hypersensitivity is antibody mediated and which are cell mediated?
Type 1,2,3 are antibody mediated
Type 4 is cell mediated
What occurs during the second encounter of the allergen in type 1 hypersensitivity?
IgE molecules bind to the antigen and mast cells or basophils release histamine
In type 1 hypersensitivity, what occurs when histamine is released?
- Vasodilation, swelling, itching, etc
- Mucous production (tears, runny nose, etc)
- Contraction of bronchial muscles causing difficulty breathing
If they antigen is spread through the body during type 1 sensitivity, what does that cause?
Sudden decrease in blood pressure (anaphylactic shock)
What are 3 treatments for type 1 hypersensitivity?
- Antihistamine
- Epinephrine
- Allergy Shot
What does an antihistamine do to treat type 1 hypersensitivity?
Blocks the action of histamine (histamine can still be produced but it does not trigger inflammation)
When does antihistamine work well?
When mild symptoms are present
Ex. Hay fever
What does epinephrine do to treat type 1 hypersensitivity?
Acts as a vasoconstrictor, increasing blood pressure. Acts for 20-30 minutes buying time for administration of an intravenous antihistamine.
What is epinephrine used to treat?
Anaphylactic shock
What does an allergy shot do to treat type 1 hypersensitivity?
Induces memory cells that produce IgG instead of IgE. IgG will and to and neutralize the antigen preventing it from binding IgE which prevents the release of histamine
How often is an allergy shot given for type 1 hypersensitivity?
Increasing doses are given over 2 years
What is type 2 hypersensitivity?
Antibody dependant cytotoxicity (needs antibody to be toxic to cells)
Antibodies are produced by foreign human cells
How is a blood transfusion an example of type 2 hypersensitivity?
- Antibodies target A and B antigens on red blood cells.
- Activates macrophages leading to phagocytosis and complement activation against the foreign cell
When can Rh factor only occur?
The second or subsequent pregnancy
What is Rh in regards to blood?
A surface antigen on rbc
When can Hemolytic Disease occur in children?
When a child is produced between an Rh- women and an Rh+ man
If a child is Rh+ with the Hemolytic Disease, what happens?
The mother can make antibodies against the Rh+ blood cells which can kill the baby after birth
Which type of hypersensitivity is caused by immune complex formations?
Type 3 Hypersensitivity
Why does type 3 hypersensitivity occur?
Occurs when there is an accumulation of immune complexes (antibody-antigen complexes) that have not be adequately cleared. They get trapped in the membrane causing problems
When would inflammation and damage to blood vessels be caused with type 3 hypersensitivity?
When complements are activated which then activates neutrophils to release enzymes
Which type of hypersensitivity is considered “delayed”?
Type 4 Hypersensitivity
Since type 4 hypersensitivity is cell mediated (not antibody mediated), what does this cause? Why?
Causes a delayed reaction 24-72 hours after contact and is caused by the activation of memory Tc cells
What are 2 examples of type 4 hypersensitivity?
Contact Dermatitis (skin rash) Poison Ivy
How is type 4 hypersensitivity caused?
When small chemicals interact with the skin proteins to form antigen, which causes a change is skin cells. The body causes a cell mediated immune response against abnormal cells, targets a localized area of the skin, then cytotoxic T cells destroy altered skin cells causing itchy, redness, etc
How is poison ivy an example of type 4 hypersensitivity?
First contact: limited response and no dermatitis results (memory T cells are produced)
Second contact: Memory T cells differentiate into activated cytotoxic T cells, causing allergic reaction (contact dermatitis)
Why when a transplant occurs, does the body want to reject the organ?
Because a cell mediated response occurs against antigenic ally different MHC molecules (the organ is attacked by T cells and natural killer cells)
In order for a transplant to be successful (the body not reject the organ), what needs to occur?
The tissues need to be closely matched, and drugs are taken to suppress the immune response
What drug is used after transplants to prevent rejection? What does it do?
Cyclosporin- prevents the colonial expansion of T cells
When transplant patients are on cyclosporin, why are they kept in isolation?
Because their immune responses are suppressed do to the cyclosporin making them extremely susceptible to infection
What are 2 types of immunodeficiency disorders?
- Primary (congenital) immunodeficiency
2. Acquired Immunodeficiency
What is an example of primary immunodeficiency? What occurs?
Severe Combined Immunodeficiency Disease (SCID)- when your T and B cells are non functional allowing for severe infections
What is an example of Acquired Immunodeficiency? Explain what happens
Acquired Immunodeficiency Syndrome (AIDS)- HIV infects and kills T helper cells, macrophages and dendritic cells. This causes the patient to be extremely susceptible to infection because both antibody and cell mediated immune responses are impaired
What does autoimmune disease mean?
When the body mounts an immune response against itself
When would autoimmune disease occur?
- In response to an infection
- Inherited
- Unknown
What are 4 types of autoimmune diseases?
- Rheumatic Fever
- Rheumatoid
- Lupus
- Multiple Sclerosis
When is Rheumatic Fever common to develop? What happens in the body?
Following strep throat
Antibodies are produced against the streptococcus M protein. Since the M protein is very similar to the heart muscle protein, the antibodies attack the heart causing tissue damage
What happens in the body that results in Rheumatoid Arthritis? What does it cause?
IgM, IgG and complement proteins act against and bind to collagen in the joints.
Causes chronic inflammation and joint pain
What happens in the body that causes Lupus?
Antibodies are produced to chromatin (complex of protein, DNA and RNA). This chromatin antibody complex accumulated in the joints, kidneys and blood vessels
What happens in the body to cause Multiple Sclerosis?
T cells and macrophages attack the myelin sheath covering neurons
What symptoms are caused from multiple sclerosis? What can trigger it?
Symptoms- mild fatigue to severe paralysis
Can be triggered by infection with the Epstein- Barr Virus
