Immune System Flashcards
What are the three phases of the immune system?
- Barrier defence
- Innate immune response
- Adaptive immune response
Describe the barrier defences of the immune system?
- skin and mucous membranes
- immediate prevention of invasion of body tissues
Describe the innate immune response?
Rapid and non specific
Describe the adaptive immune response?
Slower and specific = effective
What are the three classes of immune cells?
- Phagocytic cells
- Lymphocytes
- Cytoplasmic granules
Describe each of the three classes of immune cells?
- Phagocytic: Ingest pathogens by phagocytosis
- Lymphocytes : Coordinate activities of the adaptive immunity
- Cytoplasmic granules : mediate immune response against parasites, viruses (intracellular pathogens)
What are the primary cells of the adaptive immune response?
- Bcells
- Plasma cells
- Tcells
- Natural killer cells (NK)
What is an antibody?
Group of proteins that bind specifically to pathogen associated molecules (antigens)
What are antigens?
Chemical structures present on the surface of pathogens that bind to B/Tcell antigen receptors
Where are B-cells produced and matured?
Bone marrow + Red bone marrow
Where are T-cells produced and matured ?
Bone marrow + thymus
What is the B-cells response to antigen?
Secretes antibodies and It differentiates in to plasma cells in order to secrete soluble forms of surface antibodies.
What are plasma cells?
Activated B-cells with additional protein synthesizing machinery.
What is the T-cell response to antigens?
Doesn’t secrete antibodies
either communicates with other cells (T-Helper) using soluble factors or destroys the infected cells (cytotoxic)
What are natural killer cells?
Contain cytotoxic granules in their cytoplasm
first line of defence against viruses + cancer
What are the primary lymphoid organs?
- Bone Marrow
- Thymus
What are the secondary lymphoid organs?
- Lymph node
- Spleen
- Lymphoid nodulesv
What is the function of bone marrow?
Red: hematopoiesis
yellow: energy storage
production of B/T cells (immature)
What is the function of the thymus?
Maturation of T-cells , self vs non self development
What is the function of lymph nodes?
remove debris and pathogens from lymph
site adaptive immune response
Describe the structure of lymph nodes?
-Tough capsule of connective tissue
- sep by trabeculae
- germinal center
What is the germinal centre?
Rapid dividing B-cells surrounded by T-cells and accessory cells.
What is the function of the spleen?
remove microbes and more from blood
immune response location for blood borne pathogens
Describe the structure of the spleen?
- Divided by trabeculae
- red pulp
- white pulp
How does lymph flow through the spleen?
Enters from capillaries, collects in the venous sinuses and leaves through the splenic vein
What is red pulp and what is the purpose of red pulp?
Reticular fibres with fixed macrophages and lymphocytes
- filters blood using nonspecific immune response
What is white pulp and what is the purpose of white pulp?
(resemble lymphoid follicles)
- surround arterioles (central)
- has a germinal center
- adaptive immune response in the spleen
What are lymphoid nodules?
dense clusters of lymphocytes w/o capsule
where are lymphoid nodules located?
respiratory and digestive tracts (areas routinely exposed to pathogens)
Where are palatine tonsil located?
- inner surface of pharynx
what is the function of the tonsils?
develop immunity to oral pathogens
What is the unique structure of the palatine tonsil?
Contains invaginations of its epithelial layer called crypts which encourages accumulation/ trapping of pathogens
Where are adenoid (pharyngeal tonsils) located?
roof of the posterior superior wall of the nasopharynx
What is MALT ?
Mucosal associated lymphoid tissue, located in the underlying mucosal of the GI tract, breast tissue, lungs and eyes.
func: Immune response to ingested pathogens
What is BALT?
Bronchus associated lymphoid tissue, are lymphoid follicular structures within the respiratory tract which respond to pathogens inhaled.
What is an Epitope?
Portion of an antigen that immune response mounts to, can have multiple.
What is the sequence in defence?
1 - Innate immunity (physical barriers)
2 - Innate immunity (internal defences)
3 - Adaptive immunity
Which cells are responsible for antibody mediated immunity?
B-cells
Which cells are responsible for cell mediated immunity?
T-cells
What are self antigens?
Present on own cells as glycoproteins and glycolipids
healthy cells present MHC 1 and self antigens.
What are the two differentiations of T-cells
CD 8+ Cytotoxic T-lymphocytes
CD 4+ T-helper cells
How are lymphocytes activated?
Signal 1 - Antigen binds to antigen receptor
Signal 2 - Molecule of infected cell or the microbe binds to second receptor
Activation causes cloning of the cells which multiply specific receptors present on said antigen.
How do B-cells develop
Pre B-cell develop in yolk sac + fetal liver
Post birth = bone marrow
Naive Bcells activate trigger mitotic division
= clones to be effectors / plasma cells
= clones to remain in lymphatic tissue (memory)
What are the components of the antibody molecule?
- Light chains
- Heavy chains
- Antigen binding sites
- Complement binding sites
What are the classes of antibodies?
Immunoglobulin M,G,A
+E,D
What are the functions of antibodies?
- Distinguish self from non self
- Recognition: epitope fits on antigen binding site
- alter the shape antigen molecules to expose complement.
What occurs when epitopes bind to antigen binding sites?
- Toxic antigens are transformed into harmless substances
- agglutination for faster disposal (phagocytes)
Define chemotaxis?
Increase in neutrophils ability to move through circulation.
What is complement and what does it do?
Component of blood plasma that is activated when antibodies bind to antigen and exposes the complement binding site. causing a cascade in events leading to enzymatic functions.
MAC is a result of this.
Define MAC and what it does?
Membrane attack complexe
forms a pore on the pathogen causing ions of water to rush into the cell and causes cytolysis
Describe the antibody response time?
- IgM is released first in the early stages followed by IgG
- First response is slow and less reactive
- second response is quicker and results in high concentration of IgG.
How are T-cells developed ?
Pre T-cell are developed in the thymus into thymocytes
which go to t dependant zone (spleen + lymph nodes)
How are T-cell activated?
Require antigen to be presented to them via MHC 2 receptors and foreign antigen.
What are the differentiations of T-cells?
Effector T-cells : attack
memory T-cell : stay in bone marrow to produce more effector cells when needed. (memory)
What is the function of CD8+?
release lymphotoxins
What is the function of CD4+?
Regulate the function of Bcells, Tcells, phagocytes, other leukocytes.
What is the function of suppressor T-cells?
Suppress lymphocyte function to regulate immunity and self tolerance.
What are the stages of the adaptive immune response?
- recognition phase
- activation phase
- effector phase
- Homeostasis (decline)
- Memory
What are the defences of innate immunity?
- External barriers (skin + mucosal membrane)
- Internal defences (phagocytes, antimicrobial proteins, attack cells)
What are the peptides found in the skin and what is their function?
Defensins - protect inflamed skin from infection
what are examples of internal defences?
- fever
- chemical signals
- inflammation
What are phagocytes?
WBC that eat pathogens
What does a neutrophil do?
- consumes pathogens and selfs destructs
- makes pus
What are macrophages and what do they do?
Derived from monocytes, they can be free to patrol or fixed on fibres of an organ. Do not self destruct, (eat-digest-spit)
What are NK cells?
WBC in the blood and lymph that can kill cells infected with viruses or cancerous.
How does NK cells kill cells?
They perforate the cell with an enzyme which triggers apoptosis in the cell.
What are the stages of inflammatory response to an injury.
- Inflammation following injury, “fire alarm”
- Triggers mast cells (connective tissue) to release histamine molecules to call “alert” problem.
- Histamine = vasodilation, swelling, coagulation of vessels prev loss. allows for neutrophils and monocytes to get to location.
** Monocyte - to macrophage ** - Fight off infection by phagocytosis
What happens when lymphocytes are out numbered?
- Macrophages and release chemical signal to hypothalamus to stimulate increase in temperature (fever) to kill of pathogens
