Immunity Flashcards
What is the lymphatic system?
network of vessels
which reach almost all
tissues
What are the roles of the lymphatic system?
1) fluid recovery
2) immunity
3) lipid recovery
What is fluid recovery?
recovers fluid not picked up by cappilaries
What is immunity?
forgein materials and cells picked up in fluid
What is lipid recovery?
in small intestine
What are the components of the lymphatic system?
1) lymph
2) lymphatic vessels
3) lymphatic cells
4) lymphatic tissues
5) lymphatic organs
What is lymph?
recovered fluid
What are lymphatic vessels?
transport lymph (leaky capillaries
What are lymphatic cells?
T and B lymphocytes
NK cells
macrophages
What are lymphatic tissues?
aggregates of lymphocytes and macrophages (eg in mucosa)
What are lymphatic organs?
where lymphatic cells are connected and enclosed in connective tissue (eg red bone marrow)
What are the three lines of defences?
1) physical barriers
2) macrophages, natural killer cells, inflammation (non specific, innate immunity)
2) acquired immunity mediated by lymphocytes
What is an example of a physical barrier?
skin
What are examples of chemical barriers?
acidic pH of sweat and sebaceous secretions
fatty acids and hydrolytic enzymes
Why are mucous membranes considered barriers of defence?
mucus traps inhaled particles (dust)
watery saline layer allows cilia to push mucus to pharynx
particles do not enter cells
In what way is the body considered a hostile environment and can therefore be seen as a defence?
enzymes in saliva
acidic pH in stomach
proteolytic enzymes in bile and small intestine
What chemical defences are there in the body?
soluble factors found in blood serum include:
1) interferons (anti-viral protection)
2) complement protins (lead to pathogen destruction)
What are the two types of immunity?
1) innate immunity (first line of defence)
-rapid, non-specific, present from birth
2) acquired immunity
= recognition of ‘non self’ antigens
- mediated by B cells (antibodies) and T cells
What is innate immunity?
antigen non-specific
rapid (minutes to hours)
no memory
What does innate immunity consist of/involve?
includes physical and chemical barriers (skin)
phagocytes and natural killer cells
soluble mediators (eg complement)
pattern recognition molecules
What is adaptive immunity?
antigen specific
slow (days)
memory
What does adaptive immunity consist of/involve?
lymphocytes
antigen recognition molecules (B and T cell receptors)
secreted molecules (eg antibody)
What is the role of natural killer cells?
1) NK cells release perforins which polymerise and form a hole in the enemy cell membrane
2) granzymes from NK cell enter perforin hole and degrade enemy cell enzymes
3) enemy cell dies by apoptosis
4) macrophage engulfs and digests dying cell
What is phagocytosis?
1) Macrophage recognises a pathogen. 2) Macrophage engulfs the pathogen and forms a phagosome. 3) Lysosome fuses with phagosome. 4) Pathogen enzymatically digested.
What is acquired immune response?
specific response to antigens
capable of immunological memory
can be cell mediated or antibody mediated
recognises antigens which are non-self
What is an antigen?
molecule capable of inducing an immune response in the host organism
What are antigen presenting cells?
a heterogeneous group of immune cells that mediate the cellular immune response by processing and presenting antigens for recognition by certain lymphocytes such as T cells.
How do antigens and antigen presenting cells interact?
• Antigen presenting cells “sample” contents of the cell and present on the outside.
• Antigens are small fragments of peptide which bind to the MHC II.
• The MHC II with antigen is then moved to the
surface of the antigen presenting cell.
• When a corresponding T cell binds to the antigen it becomes activated.
What is the overall process of immune response?
1) microbes enter through break in the skin and are phagocytosed by dendritic cells
2) activated dendritic cell carries microbial peptides to local lymph node
2) activated dendritic cell activated specific T cells to respond to microbial peptides bound to MHC proteins on dendritic cell surface
3) activated cells migrate to site of infection via the blood
What are the different types of T cell?
1) naïve T cells
2) effector T cells
3) Memory T cells
What are naïve T cells?
initially bind to antigen
What are effector T cells?
usually short lived
1) Cytotoxic T cells: which can kill infected cells
2) Helper T cells: secrete cytokines to recruit more cells and to co-ordinate the attack
What are memory T cells?
remain to enable a fast response for subsequent infections by the same antigen
T cells proliferate and undergo mitosis in response to activation.
All daughter cells have T cell receptors specific to the original antigen.
These T cells remain as Memory T cells.
If you are infected with the same antigen again, memory cells allow a faster and more effective response.
What are T helper cells?
stimulate response by T and B cells
What is the difference between T and B cells?
T cells
1) bind to antigens on antigen presenting cells
2) release cytokines to recruit/activate cells tp destroy pathogen
2) antigens bind to MHC of host cells
B cells
1) bind to antigens directly on pathogens or on APCs
2) produces antibodies
3) cannot respond to intracellular pathogens
What is the process of humoral immunity?
1) antigen recognition:
2) antigen presentation:
3) clonal selection:
4) differentiation:
4) attack:
What happens during antigen recognition of humoral immunity?
immunosuppresent B cells exposed to antigen. Antigen binds only to B cells which complementary receptors
What happens during antigen presentation of humoral immunity ?
B cell internalises antigen and displays processes eptitope. Helper T cells binds to B cell and secretes interleukin.
What happens during clonal selection of humoral immunity?
interleukin stimulated B cell to divide repeatedly and form a clone
What happens during differentiation of humoral immunity?
some cells of the clone become memory B cells most differentiate into plasma cells
What happens during attack of humoral immunity?
plasma cells synthesise and secrete antibodies. Antibody employs various means to render antigen harmless
How do antibodies render antigens harmless?
1) covering pathogenic sites (neutralisation)
2) binding them together to form complexes which are harmless and can be removed or destroyed (agglutination)
3) activate a pathway of events (complement pathway) which leads to cell lysis and clearance by other cells
