Red cell antigens and functions

Red cell membrane, red cell antigens and their physilogical functions.

1. Red cell membrane and antigen functions Dr. G.D.A. Samaranayaka

2. SDS-polyacrylamide gel electrophoresis of human red blood cell (RBC) membranes. Healthy human RBC membranes stained with periodic acid-Schiff (PAS) stain

3. Red cell membrane structure

4. Schematic representation of the red cell membrane showing antigen-bearing glycosylation of proteins and lipids GPI = glycophosphatidylinositol

5. Biosynthesis of antigens of the ABO, Ii, P and Lewis systems

6. Red cell antigen functions

7. Blood group antigens on molecules important to membrane integrity Leach phenotype (absence of all Gerbich antigens). Caused by total deficiency of glycophorins C and D deficient in one or more of high frequency Gerbich antigens cause red cell shape abnormalities Rh null phenotype mild hemolytic anemia with stomatocytosis and spherocytosis McLoad phenotype protein product of the X k gene ( Kx protein) is absent acanthocytic red cells as well as a mild hemolytic anemia

8. Blood group antigens on molecules important to membrane integrity Deficiency of band 3 Band 3 protein is the most abundant red cell membrane protein. AE1 (anion channel protein) is the product of the Di locus (Diego) Determinants of the Di blood group system are associated with amino acid substitutions with band 3 Found in red cells and intercalate cells of distal and collecting tubules Crucial role in O 2 /CO 2 gas exchange between lungs and tissues. structural functions by interacting with skeletal proteins. Deficiency of band 3 in the red cells has been considered to be lethal & no Diego-null phenotype is reported

9. Transport protein Kell antigens Closely related to endothelin converting enzymes Kx a - membrane transporter structure – McLeod >20 kell antigens located on lymphocytic leukemia antigen (CALLA) Dombrock antigens Located on a glycosylphosphatidylinositol-linked protein Diego system on band 3 or the anion channel protein (AE1) Colton antigens Co a - Co b and Co 3 On a channel-forming integral protein aquaporin-1 Kidd urea transporter expressed in the endothelial cells of the renal vasarecta and the medulla

10. Adhesion receptors Members of the immunoglobulin glycoprotein super family ( IgSF ) characterized by repeating extracellular domains with sequence homology to the variable (V) and constant (C 1 or C 2 ) domain of immunoglobulins. Lutheran blood group antigens (CD 23q) - lamini receptor on both sickle red cells as well as many epithelial cancers LW protein (ICAM-4 CD24q) – bind integrins (CD11/CD18) In a and In b CD44 - leukocyte homing receptor and adhesion molecule.

11. Receptor function DARC (Duffy antigen receptor for chemokines). Bind - IL-8 and MCP-1. principally found on lymphocytes. receptor for the malarial parasite P. vivax.

12. Complement-related function Knops/McCoy blood group antigen. It is the C3b/C4b receptor aka complement receptor type 1 (CR1). important in immune adherence. Decay accelerating factor (DAF/CD55) & Membrane inhibitor of reactive lysis proteins (MIRL-CD59). Both CD55 and CD59 are attached to the membrane by. glycosylphosphatidylinositol anchors (GPI-AP). Associated with paroxysmal nocturnal hemoglobinuria (PNH).

13. Receptors on viruses and bacteria Many bacteria strains bind to a galactose-α 1 -motif shared by the blood group antigens P, P k and P 1 and are responsible for enteral and upper urinary tract infections. Glycoconjugates carrying Lewis a specificity bind B pertussis and staphylococcus aureus toxins. The receptor of parvovirus B 19 is the P glycolipid ( globoside ) on the surface of erythroid progenitors. DAF (CD55) functions as receptor for the DR. family of adhesions from E. coli strains – UTI.

14. References A Comprehensive Review of Our Current Understanding of Red Blood Cell (RBC) Glycoproteins - by Takahiko Aoki Red cell antigens: Structure and function - Abbasali Pourazar

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