Transplanting tissue and blood Flashcards
why do transplanted organs or tissues produce an immune response?
-due to the presence of non self antigens if they come form someone else
what are the two exceptions if transplants that do not produce an immune response? and why?
-transplants within the same person e/g/ skin grafts
-transplants that occur between identical twins as they are genetically identical and so have identical antigens
what is the process of transplant rejection?
-t lymphocytes are stimulated by the non self antigens on the transplanted tissue
-t cells are cloned by mitosis to form killer t cells and other cells
-the killer t cells destroy the transplanted tissue
what are the procedures that can help prevent transplant rejection?
-tissue typing
-immunosuppression techniques
-x-rays
what is tissue typing? where does the best tissue typing occur between?
-matching the donor and recipient antigens so that there is as good a match as possible e.g. little difference
-close relatives and identical twins
what are immunosuppression techniques?
-use of drugs to inhibit DNA replication which stops the cloning of lymphocytes and so stops the production of killer t cells
-for many transplants these drugs have to be taken for a very long time sometimes for life
what are x rays and how do they prevent transplant rejection? how is it used?
-used to stop the production of lymphocytes through radiation of bone marrow or lymph tissue
-this causes unpleasant side effects and so is used as a back up to immunosuppression drugs
what are the disadvantages of using immunosuppression drugs/ x rays?
-they compromise the individuals immune system
-makes them susceptible to infection as it depresses/ weakens the immune system in general
what are the three ways individuals who undergo immunosuppression techniques are protected against infection?
-anti viral drugs
-anti bacterial mouth washes
-use of monoclonal antibodies to reduce the effect of t cells involved in rejection
do red blood cells have antigen?
-yes
why are antigens for a certain blood type e.g. type A switched off during early development if the individual has type A blood?
-so that an immune reaction is not triggered
what are the 4 blood groups? and what is this categorisation an example of?
-A B AB O
-polymorphism
why can blood be donated from a donor who as type A to a recipient who also has type A?
-the recipient has no a-antibodies that correspond to the A antigens on the donor’s blood cells
why can blood not be donated from a donor who has type A to a recipient who has type B?
-the recipient has anti a- antibodies in their plasma
-the presence of the A antigens from the donors blood and the anti A- antibodies causes an antigen- antibody reaction
-this causes blood to agglutinate which blocks capillaries and can lead to organ failure or even death
what type of antigens and antibodies does blood group A have?
-A antigens
-anti B- antibodies
what type of antigens and antibodies does blood group B have?
-B antigens
-anti B- antibodies
what type of antigens and antibodies does blood group AB have?
-both A and B antigens
-neither A or B antibodies
what type of antigens and antibodies does blood group O have?
-neither A or B antigens
-both anti A and anti B antibodies
what blood groups can and cannot receive blood donation from group A and why?
-group A can (has A antigens)
-group B can’t and so will agglutinate because it has anti A- antibodies
-group AB can as it doesn’t have anti A or B antibodies
group O can’t as it has both anti A and B antibodies
what blood groups can and cannot receive blood donation from group B and why?
-group A can’t so will agglutinate as it has anti B antibodies
-group B can as it has B antigens
-AB can as it doesn’t have A or B antibodies
-O can’t as it has A and B antibodies
what blood groups can and cannot receive blood donation from group AB and why?
-both group A and B cant and will agglutinate as they contain the A and B antibodies
-AB can
-O can’t as it contains both A and B antibodies so will agglutinate
what blood groups can and cannot receive blood donation from group O and why?
-all blood groups can receive O as it doesnt contain A or B antigens
what blood group is the universal donor?
-O
what group is the universal recipient?
-AB
why do we have an ABO system? is there a best blood group?
-its thought that blood groups have mutated through time which explains why we still have these 4 blood groups
-the mutations are described as neutral as they offer not advantages to any of the blood groups
what is another blood system that doctors use?
-the Rhesus system
what is the rhesus system based on?
-the presence or absense of antigen D on red blood cells
how much of the population are rhesus positive (Rh+)?
-around 85%
what is the difference between the antibodies in the ABO system and the anti-D antibodies in the Rhesus system?
-the anti-D antibodies do not occur naturally in the blood plasma
why will someone who is Rhesus positive not produce anti-D antibodies?
-the relevant B lymphocytes will be switched off when the Rhesus positive marker is recognised as self during development
why do some Rhesus negative individuals produce anti-D antibodies?
-if their blood is contaminated with blood containing antigen D
how many a Rhesus negative’s blood become contaminated with antigen D?
-through a blood transfusion between an Rhesus positive and negative recipient
-when a Rhesus negative mother has a Rhesus positive baby
what is the sequence of events that lead to a Rhesus negative mother’s blood being contaminated by their babies Rhesus positive blood?
-during birth some of the babies RBC’s which contain antigen D leak into the mothers circulation
-causing the mother to produce anti D antibodies (by this time the baby and mother are separated so it wont cause harm to the baby)
-during future pregnancies if the baby is Rhesus positive the necessary B lymphocytes are already sensitised so will produce large amounts of anti-D antibodies quickly
-these can cross the placenta and cause agglutination of foetal RBC known as haemolytic disease of the newborn
is haemolutic disease of the newborn common today and why?
-no
-Rhesus negative mothers are given an injection of anti D antibodies during pregnancy
-which attach to babys RBC that contain antigen D that have moved to the mothers circulation before her b lymphocytes are sentised
-72hrs after birth if the baby is Rhesus positive the mother is given another injection of anti-D antibodies
