Intro to immunology Flashcards
Describe the replication time of bacteria compared to viruses?
Bacteria replicate faster than viruses
What is the basic sequence of events that occur during a viral infection?
What type of response happens initially?
- inital response is the innate immune response
-rise in type 1 interferon: interfers with replication of virus
-peak in NK (natural killer) cells: these can recognise and lyse infected cells.
these responses help to flatten virus replication
NEXT: adaptive response
-rise in cytotoxic t lymphocytes- recognise and lyse infected cells
-CTLs produce antibodies against the virus
This allows the complete removal of the virus
State some differences between innate and adaptive immune responses.
Innate:
-from birth
-relies on pre-formed and rapidly synthesised components
-limited specificity
-involves secreting cytokines to direct cells
-limited germ line encoded receptors in each individual
Adaptive/Acquired
-acquired after exposure to the pathogen
-depends on clonal selection
-slow and SPECIFIC
-GIVES immunological memory
-antibodies produced through this only
-very large number of antigen-specific receptors in each individual that are generated during lymphocyte development by recombination of gene segments.
what does the innate immune system allow and do?
- Buys time while the acquired immune system is mobilised
- evokes type 1 interferons
- activates interleukins which activate inflammatory pathways
state some cells that are part of innate and acquired immunity
eosinophils, basophils, and mast cells (filled with basophil granules)
State the two types of triggers of the innate immune response and give an example of each.
DAMP ( danger associated molecular patterns) – high extracellular ATP (becuase atp is a sign of danger as atp isnt useful outside cells
PAMP (pathogen associated molecular patterns) – bacterial cell wall components, dsRNA
What does the acute phase response respond to?
It is an inflammatory response to tissue damage.
What is a main clinical feature of the acute phase response and what causes it?
Fever – caused by Interleukin-1
Define Actue phase protein
A class of plasma proteins whose plasma concentrations increase (positive acute phase proteins) or decrease (negative acute phase proteins) in repsonse to inflammation
What are the acute phase proteins and what do they do?
C-reactive protein and serum amyloid protein: bind to molecules found on the cell wall of some bacteria and fungi
Mannan-binding lectin: binds to mannose sugar molecules which are not often found in mammalian cells.
once these proteins bind, phagocytes recognise these and ingest the agent.
The proteins are SOLUBLE PATTERN RECOGNITION RECEPTORS.
What are cytokines and do they do?
Proteins that are solube.
- a stimulus causes a cell to produce cytokines
- cytokines diffuse, bind to specific receptors and send a signal to either upregulate or downregulate proteins.
- cytokines important in proliferation of lymphocytes
What are the cells of the innate immune system?
Granular leukocytes: Natural killer cells -type of cytotoxic lymphocyte -identify and kill virus: infected cell and tumour cells Macrophages -mononuclear phagocytes -release cytokines as signals of danger Granulocytes: Basophils -release histamines -least abundant -not phagocytic Neutrophils -polymorphonuclear neutrophils (PMN) -nucleus is multi-lobed -phagocytic Eosinophils -Bi-lobed nucleus -important in immune response to parasites
Draw how to nucleus looks of:
- lymphocyte
- monocyte
- eosinophil
- basophil
- neutrophil
Look at immunology 1 : pg 58
What are antigens, immunogen and immunoglobins ?
Antigens: molecule that reacts with antibodies or T cells.
Immunogens: antigens that initate an immune response.
Immunoglobins: class of proteins
What are the five classes of immunoglobulin and what are their distinct features?
G – monomer - 75% of serum Ig. It passes from mother to foetus. Involved in the secondary immune response. A – dimer – found on mucosal surfaces – has a secretory component to resist degradation by proteases found in the mucosa
M – pentamer – has 10 binding sites so is good at agglutinating pathogens. Involved in the primary immune response -10%
E – monomer – binds to basophils and mast cells and releases histamines – involved in allergic responses
D – monomer – very low serum concentration – involved in B lymphocyte signalling.
GAMED
How do antibodies kill viruses?
- Binds to virus- prevents attachment to cell
- opsonisation- virus is coated in antibody so it can become more easily phagocytosed
- complement-mediated lysis of membrane bound virus
- Antibody Dependent cell mediated cytotoxicity-coating in antibody means that infected cells are more easily killed by NK cells by lysing the infected cells
What is the difference between B cell receptors and T cell receptors?
B cell receptors are membrane bound form of the antibody that the B cell will secrete if activated. It can bind to intact antigens.
T cell receptors can only bind to processed antigens, which are presented on MHC molecules.
T cells: there are 2 protein chains ( alpha and beta ) which together make the TCR.
Describe the process of clonal selection.
Naive lymphocytes circulate through the lymph until they meet its complementary antigen. When the lymphocyte meets its antigen it will bind and become activated and proliferate and survive. This is called clonal expansion.
What happens to lymphocytes once they have proliferated?
How does the immune system clear pathogens?
Most lymphocytes die but some survive as memory cells.
Cytotoxic T lymphocytes kill infected cell.
Destroy infected cells by injecting lethal enzymes
Antibodies bind to the pathogen and direct phagocytes to come and ingest them
What are the three main types of antigen presenting cell and what do they do?
Macrophages, Dendritic Cells, B cells – they pick up antigens and move to the lymph nodes (secondary lymphoid organs) where circulating T lymphocytes can meet the antigens.
What are the primary lymphoid organs?
Bone marrow- B cell maturation
thymus- T cell maturation
What are the secondary lymphoid organs?
Lymph nodes, Spleen, Mucosa-Associated Lymphoid Tissue (MALT)
Where are the places lymphocytes and antigen-presenting cells recirculate through lymphatic vessels:
- FRom tissues
- via lymph nodes and the spleen
- INTO the blood
how is clonal diversity generated in lymphocytes
B cells: immunoglobin gene segment
T cells: TCR gene segements
random genetic recombinations
The thymus:
Thymus function decreases slowly from puberty, which results in a reduced production of T lymphocytes and eventual immune impairment. It is simply essential for the ‘education’ of the T lymphocytes.
Artificially acquired passive immunity includes
Human intravenous immunoglobulin
Externally provided immunoglobulin is a form of passive immunity because the resident immune system is not made use of. All the other options are variations of vaccines and ALL vaccines involve the stimulation of the resident immune system to bring about an ACTIVE response.
Clonal selection is best seen in:
lymphocytes
: The spleen:
-contains red and white pulp
Germinal centres are sites of rapid B cell proliferation, and develop in response to antigenic stimulation. A blood-borne pathogen is likely to stimulate an immune response in the spleen, which therefore may contain germinal centres.
About other options: the spleen destroys redundant red blood cells, not white. Lymph nodes have lymphoid follicles rich in B cells, not T lymphocytes.
