Erythrocyte aggregation
Encyclopedia
Erythrocyte aggregation is the reversible clumping of these cells under low shear forces or at stasis. Erythrocytes aggregate in a special way, forming rouleaux
. Rouleaux are stacks of erythrocytes which form because of the unique discoid shape of the cells in vertebrate
body. The flat surface of the discoid RBCs give them a large surface area to make contact and stick to each other; thus, forming a rouleaux. Rouleaux formation takes place only in suspensions of RBC containing high-molecular, fibrilar proteins or polymers in the suspending medium. The most important protein causing rouleaux formation in plasma is fibrinogen. RBC suspended in simple salt solutions do not form rouleaux.
, results in enhanced erythrocyte aggregation.
Current experimental and theoretical evidence supports the mechanism related to the depletion of high-molecular weight molecules (e.g., fibrinogen
) for rouleau formation. This mechanism is also known as “chemiosmotic hypothesis” for aggregation.
Erythrocyte aggregation is determined by both suspending phase (blood plasma
) and cellular properties. Surface properties of erythrocytes, such as surface charge density strongly influence the extent and time course of aggregation.
which is a non-specific indicator of the presence of disease.
Influence of erythrocyte aggregation on in vivo blood flow is still a controversial issue. Enhanced aggregation affects venous hemodynamics. Erythrocyte aggregation also affects hemodynamic mechanisms in microcirculation and vascular control mechanisms.
and connective tissue
disorders, and cancers. It also occurs in diabetes mellitus
and is one of the causative factors for microvascular occlusion in diabetic retinopathy
.
Erythrocyte sedimentation rate closely reflects the extent of aggregation, therefore can be used as a measure of aggregation. Erythroyte aggregation can also be quantitated by monitoring optical properties of blood during the time course of aggregation process.
syllectometry
intravital microscopy
high-frequency ultrasound
Optical coherence tomography
Rouleaux
Rouleaux are stacks of red blood cells which form because of the unique discoid shape of the cells in vertebrate body. The flat surface of the discoid RBCs give them a large surface area to make contact and stick to each other; thus, forming a rouleau...
. Rouleaux are stacks of erythrocytes which form because of the unique discoid shape of the cells in vertebrate
Vertebrate
Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...
body. The flat surface of the discoid RBCs give them a large surface area to make contact and stick to each other; thus, forming a rouleaux. Rouleaux formation takes place only in suspensions of RBC containing high-molecular, fibrilar proteins or polymers in the suspending medium. The most important protein causing rouleaux formation in plasma is fibrinogen. RBC suspended in simple salt solutions do not form rouleaux.
Mechanism
Erythrocyte aggregation is a physiological phenomenon that takes places in normal blood under low-flow conditions or at stasis. The presence or increased concentrations of acute phase proteins, particularly fibrinogenFibrinogen
Fibrinogen is a soluble plasma glycoprotein, synthesised by the liver, that is converted by thrombin into fibrin during blood coagulation. This is achieved through processes in the coagulation cascade that activate the zymogen prothrombin to the serine protease thrombin, which is responsible for...
, results in enhanced erythrocyte aggregation.
Current experimental and theoretical evidence supports the mechanism related to the depletion of high-molecular weight molecules (e.g., fibrinogen
Fibrinogen
Fibrinogen is a soluble plasma glycoprotein, synthesised by the liver, that is converted by thrombin into fibrin during blood coagulation. This is achieved through processes in the coagulation cascade that activate the zymogen prothrombin to the serine protease thrombin, which is responsible for...
) for rouleau formation. This mechanism is also known as “chemiosmotic hypothesis” for aggregation.
Erythrocyte aggregation is determined by both suspending phase (blood plasma
Blood plasma
Blood plasma is the straw-colored liquid component of blood in which the blood cells in whole blood are normally suspended. It makes up about 55% of the total blood volume. It is the intravascular fluid part of extracellular fluid...
) and cellular properties. Surface properties of erythrocytes, such as surface charge density strongly influence the extent and time course of aggregation.
Effects
Erythrocyte aggregation is the main determinant of blood viscosity at low shear rate. Rouleau formation also determines Erythrocyte sedimentation rateErythrocyte sedimentation rate
The erythrocyte sedimentation rate , also called a sedimentation rate or Biernacki Reaction, is the rate at which red blood cells sediment in a period of 1 hour...
which is a non-specific indicator of the presence of disease.
Influence of erythrocyte aggregation on in vivo blood flow is still a controversial issue. Enhanced aggregation affects venous hemodynamics. Erythrocyte aggregation also affects hemodynamic mechanisms in microcirculation and vascular control mechanisms.
Causes
Conditions which cause increased rouleaux formation include infections, inflammatoryInflammation
Inflammation is part of the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. Inflammation is a protective attempt by the organism to remove the injurious stimuli and to initiate the healing process...
and connective tissue
Connective tissue
"Connective tissue" is a fibrous tissue. It is one of the four traditional classes of tissues . Connective Tissue is found throughout the body.In fact the whole framework of the skeleton and the different specialized connective tissues from the crown of the head to the toes determine the form of...
disorders, and cancers. It also occurs in diabetes mellitus
Diabetes mellitus
Diabetes mellitus, often simply referred to as diabetes, is a group of metabolic diseases in which a person has high blood sugar, either because the body does not produce enough insulin, or because cells do not respond to the insulin that is produced...
and is one of the causative factors for microvascular occlusion in diabetic retinopathy
Diabetic retinopathy
Diabetic retinopathy is retinopathy caused by complications of diabetes mellitus, which can eventually lead to blindness....
.
Erythrocyte sedimentation rate closely reflects the extent of aggregation, therefore can be used as a measure of aggregation. Erythroyte aggregation can also be quantitated by monitoring optical properties of blood during the time course of aggregation process.
Mesurement
blood filmBlood film
A blood film or peripheral blood smear is a thin layer of blood smeared on a microscope slide and then stained in such a way to allow the various blood cells to be examined microscopically...
syllectometry
intravital microscopy
Intravital microscopy
Intravital microscopy is a technique used to observe biological systems in vivo at high resolution through an attached window preparation. It is a type of microscopy....
high-frequency ultrasound
Optical coherence tomography