Rouleaux

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Typical mammalian erythrocytes: (a) seen from surface; (b) in profile, forming rouleaux; (c) rendered spherical by water; (d) rendered crenate by salt. (c) and (d) do not normally occur in the body.

Rouleaux (singular is rouleau) are stacks of red blood cells (RBCs) 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 rouleux. They occur when the plasma protein concentration is high, and because of them the ESR (erythrocyte sedimentation rate) is also increased. This is a non-specific indicator of the presence of disease. ^[1]

Conditions which cause rouleaux formation include infections, inflammatory 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.

The presence of acute phase proteins, particularly fibrinogen, interacts with sialic acid on the surface of RBC and allows the formation of rouleaux. Anaemia, by altering the ratio of RBC to plasma, increases rouleaux formation and accelerates 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. in the guinea pig.

Kinetics of Linear Rouleaux Formation

According to Smoluchowski, the kinetics of aggregation 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. 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.

External links

• Rouleaux: Presented by the University of Virginia

References

• http://bloodjournal.hematologylibrary.org/cgi/content/full/107/11/4205
• http://www.biophysj.org/cgi/content/full/78/5/2470