L.O – Describe the use of antibodies and the making of vaccines

ABO Blood groups In 1900 Karl Landsteiner discovered that human blood differed from one individual to another. This difference is due to the presence of antigens on the plasma membranes of red blood cells and on the presence or absence of antibodies in plasma.

GENES & BLOOD TYPE

PROTEINS & BLOOD TYPES Antigens are attached to the surface of red blood cells. There are two different types of antigens: i.Type "A" and ii.Type "B". Each type has different properties. The ABO blood type classification system uses the presence or absence of these molecules to categorize blood into four types: A, B, AB & O.

Blood Groups 4 types – A, B, AB and O Named according to the antigens which are present on the surface of the red blood cell. Another level of specificity is added to blood type by examining the presence or absence of the Rh protein. Each blood type is either positive "+" (has the Rh protein) or negative "-" (no Rh protein). For example, a person whose blood type is "A positive" (A +), has both type A and Rh proteins on the surface of their red blood cells.

Two copies of the gene are inherited, one from each parent. The possible combinations of alleles produce blood types in the following way;

Blood groups a person with a specific antigen on their red blood cells does not possess the corresponding antibody in their plasma. when a patient receives a blood transfusion it is vital that the blood is compatible with his own.

ABO blood groups blood groupOABAB % population (european) antigen-ABA + B antibodyanti-a anti-b anti-a-

WHEN BLOOD TYPES MIX

Blood transfusion ABABO A x x B x x AB xx x O donor recipient safe transfusion ( ) (no agglutination) unsafe transfusion (x) (agglutination)

Agglutination If a person is given a donation of blood from the wrong group, then the red blood cells from the donor’s blood will be clumped or agglutinated by the antibodies in the recipients plasma. The agglutinated red cells can block blood vessels and stop the circulation of blood to various parts of the body. Agglutinated blood cells can also break open so that their contents leaks out. Haemoglobin becomes toxic when it is outside of the cell and can kill.

Blood Groups in Pregnancy Rhesus blood groups do not usually cause any problems, however, they can do during pregnancy. A rhesus negative mother could carry a rhesus positive baby if her partner was. During pregnancy, the blood from the mother and baby do not mix, but towards the end of the pregnancy or during birth the placenta can start to break down and a few red blood cells can leak. These are treated as foreign cells and antibodies are stimulated against them. This should not harm the baby as it happens right at the end of the pregnancy. However, if the mother goes on to have another rhesus positive baby, the antibodies have been made previously and can therefore pass across the placenta and destroy the fetal red blood cells. If left untreated, the baby can be born with haemolytic disease or may even be stillborn.

Blood Groups in Pregnancy. Haemolytic disease of the newborn used to be treated by giving the baby a total blood transfusion at birth, but it can now be prevented. Pregnant women who are rhesus negative are given an injection of anti-rhesus globulin early in pregnancy to stop them making anti rhesus antibodies.

H/wk – due Monday Research and explain why it has not yet been possible to develop a vaccine against HIV. Explain how antibodies can be used to test for HIV and TB.