This article is about red blood cell stacks. "Rouleaux" is a plural form for "Rouleau". For people, see
Rouleau (surname). For other uses, see
Rouleau.
Rouleaux (singular is rouleau) are stacks or aggregations of
red blood cells (RBCs) that form because of the unique
discoid shape of the cells in
vertebrates. The flat surface of the discoid RBCs gives them a large surface area to make contact with and stick to each other; thus forming a rouleau. They occur when the plasma
protein concentration is high, and, because of them, the ESR (
erythrocyte sedimentation rate) is also increased. This is a nonspecific indicator of the presence of disease.[1]
Conversely, the presence of rouleaux is a cause of disease because it will restrict the flow of blood throughout the body because capillaries can only accept free-flowing singular and independent red blood cells. The aggregations, also known as "clumping," form as an allergic reaction to certain antibiotics and not necessarily because of disease.
Acute-phase proteins, particularly
fibrinogen, interact with
sialic acid on the surface of RBCs to facilitate the formation of rouleaux. An increase in the ratio of RBCs to
plasma volume, as seen in the setting of
polycythemia and hypovolemia, decreases rouleaux formation and decreases sedimentation.
Rouleaux formation is retarded by
albumin proteins.
Rouleaux formations are also adopted by
spermatozoa as a means of cooperation between genetically similar gametocytes so as to improve reproductive success through enhanced motility and, therefore, fertilization capacity—e.g., the
guinea pig.
Kinetics of Linear Rouleaux Formation
According to
Smoluchowski aggregation, the
kinetics of colloids is based on the assumption that each particle is surrounded by a "sphere influence". Single spherical particles which undergo
Brownian motion collide and sticking of particles happens. As aggregation proceeds, the average diffusion constant of the aggregate population decreases. The aggregation of red blood cells progresses in the same manner except that cells are
biconcave rather than spherical.