DISORDERS OF THE RED CELL MEMBRANE
1. The Red Cell Membrane
The red cell membrane consists of a lipid bilayer, a variety of proteins studded therein, and the glycans that stick outward, being linked covalently either to proteins or to lipids. Protein or glycan domains constitute the structural bases of blood groups.
A schematic picture of the red cell membrane is shown below.
1.1 The most important structural red cell proteins
The band 3 complex
The protein 4.1 complex
The Rh complex
The protein interactions are shown below
In the red cell membrane Rafts are detergent-resistant plasma membrane microdomains. They are rich in sphingolipids. They are also rich in cholesterol. They exist as islets having a phase different to that of the loosely packed disordered state of the rest of the bilayer. Shingolipids long, largely saturated fatty acid allowing them to pack tightly together.
Lipid rafts show a higher density of some proteins, such as phosphatidyl-inositol linked proteins, stomatin and flotillin-1 and -2.
Related to lipid raft are caveolae, which are invaginated plasma membrane microdomains. Flotillins may act as scaffolding proteins within caveolar membranes.
1.2 Blood group antigens
Blood group antigens are surface markers on the red blood cell membrane
The most important antigens for blood transfusion are the ABO system and Rh, Kell, Duffy, and Kidd antigens.
2. Genetic disorders affecting the mechanical properties of the red cell
The main genetic disorders affecting the mechanical properties of the red cell are hereditary spherocytosis (HS) and hereditary elliptocytosis (HE)
3. Genetic disorders affecting blood group components
The red cell membrane is comprised of a lipid bilayer
studded with transmembrane proteins, and laminated by a protein
network, the membrane skeleton, at the surface of the inner
3.1 Rh-deficiency Syndrome
Rh-deficiency is a rare autosomal recessive condition, which results from the lack (Rh null) or severe reduction ( Rh mod) of the red cell Rh and LW antigenes, and, to a variable extent,of the other accessory chains ( CD47 , GPB) of the red complex. Rh deficient phenotypes are caused by several different mutations that occur in either the RHAG or RH loci on chromosome 6p12-p21 and 1p34-p36, respectively.
3.2 McLeod Syndrome
McLeod is rare phenotype initially described as an X-linked trait in which red cells lack the common Kx antigen and have a marked decrease in all blood group Kell antigens.