Overview Of The Immune System Flashcards
(33 cards)
What is the immune system and what does the immune system use?
- The immune system protects the body against pathogens (disease causing organisms) such as virus, bacteria, parasite and fungi.
- The immune system uses a complex series of protective mechanisms (cells, tissues and organs)to control and eliminate pathogens.
- The immune system constantly adapts to deal with the different pathogens
What is one of the main abilities of the immune system and how is it achieved?
- They have an ability to differentiate between the bod’s own cells (Self) and foreign cells (non self) e.g. blood type- someone can’t be given a blood type which doesn’t belong to them.
- This is achieved through self marker molecules associated with the surface of body cell. When the immune system encounters cells carrying ‘foreign’ molecules it mounts an attack.
What is an antigen?
-An antigen is anything which triggers an immune response (could be part of a microbe or foreign cells)
What are 4 types of pathogens and their size?
- Virus (10-1000 nanometers)
- Bacteria (0.1-5 micrometres)
- Protozoa (parasite; 5-200 micrometres; they can get big enough to see with the naked eye and can be seen with a microscope with a low resolution)
- Fungi (3 micrometers - 1 millimeter)
What is and causes sty, conjunctivitis, bacterial infection of cornea, herphsintex and acanthomeba
- Sty- infection of glands at base of eyelids
- conjunctivitis- caused by bacteria and virus and due to the constant opening of the eye, it is more exposed to these bacteria and virus.
- Bacterial infection of cornea- usually due to contact lenses- can lead to loss of vision
-
What is and causes sty, conjunctivitis, bacterial infection of cornea, herphsintex and acanthomeba
- Sty- infection of glands at base of eyelids
- conjunctivitis- caused by bacteria and virus and due to the constant opening of the eye, it is more exposed to these bacteria and virus.
- Bacterial infection of cornea- usually due to contact lenses- can lead to loss of vision
- Herphsintex- this is a virus and can cause cold sores
- acanthomeba- this is caused by a protozoa and is a corneal infection
What is the lifestyle of microbes e.g are they intra or extracellular
- Virus are intracellular but can be extracellular- they don’t have the capacity for independent division therefore called intracellular virus and hijack cells in body and tell it to replicate it’s bad RNA.
- Bacteria is largely extracellular as they spend most of their time outside of the cell therefore accessible to immune system and easier to deal with than virus.
- protozoa can be intra and extracellular. an example is malaria
- Fungi is extracellular
What two overlapping compartments does the immune system consist of?
- Innate immune system- it is the first line of defense of series of physical barriers to prevent entry of pathogens, cause phagocytes to digest microorganisms and tell chemical mediators to trigger recruitment and activation of immune cells (inflammation). It is unsophisticated.
- Adaptive system- : is formed principally by lymphocytes (T and B cells) which contain specific receptors to recognize specific antigens associated with pathogens. Also retains memory of previous encounter with the pathogen. Has property of specificity- can recognize pathogens very easily and differentiate between them
What can the immune system be split into?
- it can be split into innate (non specific) or adaptive.
- Innate (non specific) can be split into external defences or internal defences
- Adaptive (specific) can be split into antibody mediated or cell mediated
FOR DIAGRAM REFER TO SLIDE 8 OF LEC 7
What are some examples of innate (non specific) barriers to infection?
- The skin- it is impermeable to most infectious agents due to 2 reasons;
- Acidic skin secretions
- Desquamation of skin cells remove potential pathogens
- Acidic skin secretions
- Mucus secreted by membranes lining the inner surface of the body block the attachment of microbes to epithelial cells.
- Washing action of tears. saliva and urine also limit attachment
- Many secreted body fluids contain antibacterial components e.g. acid in stomach, lysozyme in tears and saliva
- Many non pathogenic microorganisms are present on the external and internal surfaces of the body where they compete for essential nutrients (commensals- these are friendly bacteria but compete with other bacteria to get nutrients.
What is the process of the innate barriers after a microorganism enters the body?
- Once they penetrate, they can be destroyed via phagocytosis
What do phagocytes include?
-They include polymorphonuclear neutrophils and macrophages
What are neutrophils?
-They are the predominant white cell in the bloodstream but can migrate into tissues during inflammation.
What is the process of phagocytosis in the internal innate defence?
- Macrophages differentiate from blood monocytes
- mature macrophages settle in tissues where they are strategically placed to intercept microbes
- Phagocytes arrive at side of inflammation by chemotaxis
- phagocytes bind to microorganism via surface receptors, internalize them (by a phagosome) and kill them (by a phagolysosome)
What is the role of the complement system and how does it get activated?
- The complement system comprises over 30 cell associated and soluble proteins
- Activation of complement begins with recognition proteins which bind pathogens, or structures associated with cellular damage/debris
- Complement activation leads to a coordinated cascade (cascade is best for doing something fast and amplified) of enzymatic cleavage events generating complement protein fragments that carry out particular functions such as;
- Recruit phagocytes
- Enhance phagocytosis (‘opsonisation’)
- Membrane damage to foreign cells or microbes
What are Natural Killer (NK) cells?
- Some lymphocytes are neither T or B cells. They are NK cells because they are specialised to kill certain types of target cells such as;
- Virally infected cells
- Tumour cells
What is the purpose of the adaptive (specific) immune response
- Microorganisms develop strategies to evade the innate defence mechanisms therefore the body has devised defence mechanisms which are tailored to deal with specific microbes
- These mechanisms have both specificity and memory
- The cellular basis of specific immunity is provided by lymphocytes
Where do lymphocytes originate from and where do T and B cells develop?
- All lymphocytes originate from stem cells in the bone marrow
- B cells development occurs in the bone marrow
- T cells develop in the thymus
What are primary lymphoid tissue?
-The bone marrow and thymus constitute primary lymphoid tissue where T and B cells differentiate into mature antigen recognising cells
What are secondary lymphoid tissue?
-Secondary lymphoid tissues are those in which lymphocyte activation, proliferation and differentiation occurs
What are lymphocytes examples of, responsible for, and what are the types of lymphocytes?
- Lymphocytes are examples of adaptive (specific) immune response
They are responsible for recognizing molecules of infecting pathogens (antigens which stimulate the immune response)
- There are two classes of lymphocyte: T and B cells:
- B cells are concerned with the control of extracellular infections. They use cell surface antibodies as antigen receptors
- T cells are concerned with intracellular infections. They use specialised T cell receptors (TCR).
-Each T cell and B cell can recognise only one particular antigen.
What does a large lymphocyte population ensure?
-It ensures that an enormous range of antigens can be recognised by the body
What is clonal selection?
- Following first contact with pathogen the immune system must expand the number of cells which recognize that pathogen.
- Following recognition of the pathogen the immune system must mount an appropriate response to eliminate it and minimize the damage it causes
- Memory cells confer lasting immunity to the particular pathogen
What is the B cell response?
- B cells recognize antigen through an antibody receptor on their surface (this is their main role)
- Following encounter with antigen, B cells transform in to antibody-producing cells (plasma cells)
- The formation of memory B cells provides an enhanced response on repeat exposure
