Blood Groups

what are blood groups

glycoproteins and glycolipids acting as antigens on red blood cell surfaces

why are blood groups important

blood transfusion, relationship testing

blood transfusion

matching blood types prevents hypersensitivity reactions which could have serious/fatal results

relationship testing

blood groups follow mendelian inheritance so where used historically for paternity testing

blood groups

A, B, AB, O, decided by A and B glycolipid antigens on red blood cells

Type A

A antigen, Anti - B plasma antibodies, can receive A or O blood

Type B

B antigen, Anti - A plasma antibodies, can receive B or O blood

Type AB

both A and B antigens, no antibodies, can receive any

Type O

no A or B antigens, Anti - A and B plasma antibodies, only receive O but universal donor

ABO antigens

naturally occurring antigens, present without transfusion or exposure, IgM, likely triggered by food or gut bacteria

D antigen

rhesus blood group system on surface of red blood surface

what happens if a Rh- person is exposed to Rh+ RBCs

their immune system may produce anti - D antibodies, called sensitisation

why are RhD important

blood transfusions and pregnancy

why is RhD important in pregnancy

they are IgG antibodies so can cause haemolytic transfusion reactions, HDFN

IgG antibodies

can cross the placenta

HDFN

haemolytic disease of the foetus and new born

HDFN cause

can occur when Rh- mother is carrying a Rh+ baby

first pregnancy Rh- mother, Rh+ baby

Rh+ foetal cells enter mother’s circulation, mother may become sensitised and produce anti - D antibodies

second pregnancy Rh- mother, Rh+ baby

mother’s anti - D IgG cross placenta, attach to babies RBC, babies RBC are destroyed

when does sensitisation of mother occur

late in first pregnancy, around delivery, no affect on first Rh+ baby

HDFN effects

jaundice from increased bilirubin, anaemia from lack of RBC, possibly serious or fatal

HDFN treatment

phototherapy, blood transfusion, exchange transfusion

phototherapy

helps reduce bilirubin, jaundice

blood transfusion

treats significant anaemia

HDFN prevention

Rh- mothers can be given anti-D immunoglobin

anti-D immunoglobin

removes Rh+ foetal cells from the mother’s circulation before her immune system is sensitised, prevents mother developing her own anti-D