THE RED CELL MEMBRANEBLOOD BANKING
Prepared by:JOSEPHINE C. MILAN, RMT, MSMT
DEPARTMENT OF MEDICAL LABORATORY TECHNOLOGY
UNIVERSITY OF TABUK
OBJECTIVE and FOCUSTo correlate the structure of the red cell membrane with the occurrence of blood group antigens and how it is influenced by storage conditions.
RATIONALEQ: WHY DO WE STUDY THIS TOPIC ?The main purpose of blood transfusion is to supply
red cells which should remain viable and functional in the transfused patient/ recipient.
We have to understand the nature of RC membranes.
Mainly, blood groups antigens are located in /on the red cell membranes. The structure of the red cell membranes has certain roles for its functionality. There are important things to remember about the characteristics of red cell membranes.
TOPIC OUTLINE (based on syllabus)1. Red cell membrane structure2. Blood group antigens on the red cell
membrane3. Other properties of the red cell membrane
Main reference: Modern Blood Banking and Transfusion Practices by Denise M. Harmening. F.A. Davis Company. Philadelphia 5th ed
RED CELL FUNCTIONMain function of red cells:
To transport oxygen to tissues, and bind carbon dioxide from
tissues to be brought to the lungs for excretion.
Important for RBC survival and function:
1. normal chemical composition and structure of the RBC membrane
2. hemoglobin structure and function
3. RBC metabolism
RED CELL MEMBRANE STRUCTURE
RBC Membrane:
1. RBC membrane is a semipermeable lipid bilayer
supported by a protein meshlike cytoskeleton structure.
2 layer of lipids
proteins
RED CELL MEMBRANE STRUCTURE
2. Behaves as semisolid, with elastic and
viscous properties
important and critical for survival in the
circulation for 120 days going through numerous
cycles and passages through narrow veins and
sinusoids in the spleen.
in RBC deformability and permeability (crucial /
critical characteristics)
Biochemical structure
3. The cell membrane consists of :
protein,
lipids, and
carbohydrates
Ratio of- 52 (P) : 40 (L) :
8 (C)
PROTEINS IN THE MEMBRANEProteins : form a meshwork that traverse the lipid bilayer,
called membrane skeleton
2 types of proteins:
a. “integral” membrane proteins-which are in contact
with both sides of the membrane; provides anion
channels through the RBC membrane
b. “peripheral” proteins – located and limited to the
cytoplasmic/inner surface of the membrane forming the
RBC cytoskeleton; gives the cell its biconcave structure
Types of membrane PROTEINS
Integral Proteins Peripheral Proteins
Glycophorin A
Glycophorin B
Glycophorin C
Anion- exchange channel
protein
(band 3)
Spectrin
Actin (band5)
Ankyrin (band 2.1)
Band 4.1 and 4.2
Band 6
Adducin
jcm 11/2008
LIPIDS on the membrane phospholipids = 50 %;
cholesterol = 40 %;
glycolipids = 10 %
PHOSPHOLIPIDS form a bilayer
hydrophobic (nonpolar) tails towards inside of cell
hydrophilic (polar) head groups towards outside (extracellular)
or the inside (cytoplasmic ) surface
the outer leaflet (external layer) contains electrically neutral
glycolipids and choline phospholipids; while
the inner leaflet (internal cytoplasmic layer) predominantly
contains phosphatidyl serine which is negatively charged.
CARBOHYDRATES on the membrane
Carbohydrates : forms the glycocalyx,
serving as a negatively charged barrier ,
around the outside of the RBC membrane.
important in preventing cells from
adhering (attachment) to one another, or
adhering to the endothelium (vein wall)
BLOOD GROUP ANTIGENS on the RC membrane
Majority carried on transmembrane proteins
Few antigens carried on glycosylphosphatidyl -
inositol (GPI)- linked proteins or on glycolipids
Some transmembrane proteins interact with other
transmembrane proteins
Ex: (band 3 and GPA) like Kell and Kx, Rh and RhAG
Some antigens are adsorbed from plasma : Lewis,
Chido
PROPERTIES of RC membraneRBCs are biconcave disks, mean diameter of
7-8 µmHave more surface area than volume, which
creates a soft, pliable cell.Mature cells have no nucleus or
mitochondria, but it is packed with enough metabolism to exist for 120 days.
PROPERTIES of RC membraneDEFORMABILITY
red cell must be easily deformed/change shape advantageous when these pass through small openings or
channels, as in the spleen
Causes of loss of deformability / rigidity of cell :
Loss of ATP decreased phosphorylation of spectrin
Increase deposition of calcium onto cells
examples : spherocytes, “bite cells”
cell become easily lyzed
PERMEABILITY
important to prevent colloidal hemolysis and control the
volume of RBC:
favorable to active cation transport
permeable to water and anions, like chlorides and
bicarbonate
relatively impermeable to cations like Na and K
Intracellular : extracellular ratio of Na -1:12;
K -25:1
cationic pump for active transport (requiring ATP) of Na
and K .
Ca is transported outward from cell, depends on Ca-
ATPase pump
Calmodulin ( calcium-binding protein)- control the
ATPase pump; prevent excessive intracellular buildup
which leads to rigidity.
When ATP is depleted, Na and Ca accumulate
intracellularly, K and water get out of the cell
dehydration and rigidity of cell easily sequestered
(trapped) in the spleen , thus decrease in RBC survival.