Immunology Flashcards
First line of defense
Mechanical barriers such as the skin and mucous membranes.
All other non-specific defenses are part of the second line of defense.
Second line of defense: Chemical barriers
- Enzymes in body fluids such as pepsin in the stomach and lysozyme found in tears that ruptures bacterial cell walls.
- Inferferons block viral replication
- Defensins are produced by neutrophils that make holes in bacterial cell walls.
- Collectins are proteins that protect against my bacteria, yeast, and virus. Precursor to complement.
- Complement is a group of proteins in plasma that stimulates inflammation.
Interferons and complement both
Play a roll in stimulating or attracting phagocytes for phagocytosis.
Are NK cells innate or active immunity?
Innate. They defend against viruses and cancer cells by secreting performs that lyse cell membranes.
Perforins
Secreted by NK to lyse cell membranes of cells with cancer or viruses inside.
The 4 signs of inflammation
Rubor- redness
Dolor- pain
Calor- Heat
Tumor- Swelling
Sepsis
When infection spreads to other parts of the body
Major 6 actions of an inflammation response
- Blood vessels dilate, causing tissues to show 4 signs of inflammation.
- White blood cells invade. Neutrophils.
- Clotting factors seep into the area, forming clot of fibrin,
- Fibroblasts arrive to form a CT sac around the injured tissues.
- Phagocytes are active and remove bacteria/dead cells.
- Cells divide to replace old injured cells.
The most active phagocytic cells are
Neutrophils and monocytes (macrophages and dendritic cells)
Chemotaxis
Chemicals from damaged tissue attract phagocytic cells to site of injury.
Monocytes that leave the blood become
Macrophages- can either be free or fixed in tissues.
What stimulates a fever
Interleukin-1 (IL-1). Stimulated when infection stimulates lymphocytes to proliferate.
How many T, B, and NK cells in the blood
70-80% are T cells
20-30% are B cells
1% are NK cells
T cell origin
Created in the bone marrow and mature in the thymus. Most go on to roam in the blood, but some settle in lymph nodes, thoracic duct, and white pulp of spleen.
B cell origin
Created in the bone marrow and mature in the bone marrow. Go to the blood, lymphatic organs, and intestinal linings and tonsils.
T helper cells interacts with cytotoxic T cell that has been combined with an identical antigen by
Interleukin-2. This activates cytotoxic T cells to proliferate into memory T cells and more cytotoxic T cells.
T helper cell interacts with B cell that has been combined with an identical antigen by
Cytokines. This activates the B cell so it is able to proliferate into plasma (effector) cells and memory cells.
4 types of cytokines
CSF- stimulates bone marrow to produce more lymphocytes.
Interferons- Block viral replication and attack viral cells/cancer cells.
Interleukins- Control lymphocyte differentiation and proliferation. Also can cause fever. Controlled by T cells.
TNF- Stops tumor growth and releases growth factors
Once B cells bind to their Ag, what happens?
They have to wait for approval by T helper cells. T helper cells also activated will release cytokines that allow the B cell to proliferate into plasma (effector) and memory cells.
Humoral immunity vs cellular immunity
B cells have humoral immunity (indirect) by Abs and T cells have cellular immunity
Antibody is composed of
2 light chains (outer) and 2 heavy chains. The top of the Y on both the heavy and light chains are called the variable regions.
5 major type of antibodies and their percentages
IgG- 80% IgA- 13% IgM - 6% IgD- less than 1% IgE- less than 1%
Where is IgG located and what is it’s major functions?
Makes up 80% of all Ab
Located in the plasma and tissue fluid
Defends against bacteria, viruses, and toxins.
Can activate complement.
Where is IgA located and what is it’s major functions?
Makes up 13% of all Ab
Located in exocrine gland secretions. Defends against bacteria and viruses in mucous membranes.
Where is IgM located and what is it’s major functions?
Makes up 6% of all Ab
Located in the plasma
Reacts with antigens on some red blood cell membranes following mismatched blood transfusions.
Activates complement.
Which two Antibodies can activate complement
IgG and IgM
Where is IgD located and what is it’s major functions?
Less than 1% of all Ab
Found on the surface of most B cells
Helps with B cell activation
Where is IgE located and what is it’s major functions?
Makes up less than 1% of all Ab
Found in the exocrine gland secretions/mast cells.
Promotes inflammation and allergic responses.
Which two Antibodies are located in exocrine gland secretions?
IgA and IgE
Antibodies react to antigens in which 3 main ways?
- Direct attack on antigens
- Activation of complement
- Stimulation of inflammation, to help prevent the spread of infection.
3 ways that antibodies can directly attack an antigen?
- Agglutination.
- Precipitation- antigens and antibodies become insoluble so the antigen cannot work properly.
- Neutralization. Antigens lose toxic properties.
Opsonization
Marking a cell for phagocytosis by flagging it with a protein receptor.
Complement can alter antigen cell membranes so cells are more susceptible to phagocytosis
Primary immune response. First antibodies appear in how many days? How long do they remain in the body for?
- The first antibodies appear in 5-7 days. Takes time for T cells to become activated and activate B cells.
- Antibodies remain in the body for 5-10 days
- memory B and T cells are produced and remain for life basically
Secondary immune response. Subsequent exposure to antigen produces high concentration of antibodies in how many days? Ab remain in body for how long?
Produces high concentration of antibodies in 1-2 days. Antibodies remain in the body for months or years after. and memory B/T cells remain for life basically.
Examples of naturally acquired active immunity
Exposure to live pathogens. Result in an immune response with symptoms of a disease.
Examples of artificially acquired active immunity
Vaccine containing weakened or dead pathogens. Results in a stimulation of an immune response without symptoms of a disease.
Examples of naturally acquired passive immunity
Antibodies passed to fetus from pregnant women with active immunity or to newborn through colostrum or breast milk. Short-term immunity for a newborn without stimulating an immune response.
Examples of artificially acquired active immunity
Injection of antiserum containing specific antibodies or antitoxin. Short-term immunity without stimulating an immune response.
4 types of hypersensitivity reactions
Type 1- immediate reaction involving IgE
Type 2- antibody binds antigen cand causes complement
Type 3- Immune complex reaction resulting in complement and damages to nearby tissues
Type 4- Delayed reaction hypersensitivity. Involves T cell activation, which is why it takes about 48 hours.
Type I hypersensitivity.
- Immediate reaction
- Ex: hay fever
- Initial contact with antigen produces IgE antibodies that attach to mast cells.
- Subsequent exposure results in the degranulation of mast cells, releasing histamine.
- Symptoms include hives, hay fever, asthma, anaphylactic shock.
Type II hypersensitivity
Antibody dependent cytotoxic reaction.
- Ex: Mismatched blood transfusion
- Antigen binds to a specific cell, causes phagocytosis and induces complement.
Type III hypersensitivity
Immune-complex reaction
- Ex: Rheumatoid arthritis/autoimmune diseases
- Antigen-antibody complexes form and deposit in certain tissues. Damages tissues due to phagocytosis and complement.
- Antibody complexes cannot be cleared from the body
Type IV hypersensitivity
Delayed-reaction hypersensitivity
- Ex: Dermatitis
- Can affect anyone
- Results from repeated exposure of skin to allergen. Allergen activates T cells in skin, which release chemicals that cause inflammation.
- Takes 48 hours to occur.
Important to match the ___ antigens between the donor and recipient. The greater the difference, the faster and stronger the graft will be rejected
MHC/HLA
4 types of grafts and which are most successful
- Autograft- self to self. From other parts of the body.
- Isograft- from an identical twin
- Allograft- From the same species (Kidney transplant from donor)
- Xenograft- From a different species. (heart valves from pig)
Most successful are autografts and isografts
When the immune system fails to distinguish self from non self, they produce antibodies called
Autoantibodies
As we age, what immune organ decreases in size
The thymus decreases about 25%
With age, do T and B cell numbers change? Does their activity level change?
T cell count decrease slightly
B cell count remains the same
Activity level declines in both
How do levels of antibodies change with age?
IgA and IgG increase
IgD stays the same (if they are on B cells and B cell levels stay the same)
IgE and IgM decrease
