transfusion medicine Transfusion medicine (or transfusiology) is the branch of medicine that encompasses all aspects of the Blood transfusion, transfusion of blood and blood components including aspects related to hemovigilance. It includes issues of blood donation, im ...

, mixed-field agglutination refers to mixed reactions during cell typing where two distinct cell populations are present: agglutinated cells admixed with many unagglutinated cells. The presence of two or more cell populations is known as

chimerism A genetic chimerism or chimera ( or ) is a single organism composed of cells of different genotype, genotypes. Animal chimeras can be produced by the fusion of two (or more) embryos. In plants and some animal chimeras, Mosaic (genetics), mos ...

. Mixed-field agglutination is an important cause of ABO typing and genotype discrepancies. The cause of mixed field agglutinations should be sought prior to setting up blood for transfusion.

Causes

False chimerism

By far the most common cause of mixed-field agglutination is false chimerism. There are several causes of false chimerism; 1) Transfusion of donor red cells. For example, a blood group B individual who has received a transfusion of group O donor red cells may show mixed field agglutination with anti-B sera. His own group B red cells are agglutinated by the anti-B sera while the group O donor red cells in his circulation are unagglutinated 2) After an ABO mismatched

stem cell transplant Hematopoietic stem-cell transplantation (HSCT) is the transplantation of multipotent hematopoietic stem cells, usually derived from bone marrow, peripheral blood, or umbilical cord blood, in order to replicate inside a patient and produce a ...

for example a blood group O stem cell donor and a blood group A stem cell recipient.Bluth MH, Reid ME, Manny N. Chimerism in the immunohematology laboratory in the molecular bioplogy era. Transfus Med Rev 2007;21:134-46. 3) Weak expression of the A or B blood group

antigen In immunology, an antigen (Ag) is a molecule, moiety, foreign particulate matter, or an allergen, such as pollen, that can bind to a specific antibody or T-cell receptor. The presence of antigens in the body may trigger an immune response. ...

4) In some diseases, for example leukaemia

True chimerism

A true chimerism is a rare sporadic phenomenon whereby an individual has a dual cell population derived from more than one zygote. This may result from intrauterine exchange of erythrocyte precursors between twins (twin chimerism) or two fertilized eggs fuse into one individual. Twin chimerism results from mixing of blood between two twin fetuses through placental blood vessel anastomoses, leading to engraftment of hematopoietic stem cells from one twin within the marrow of the other. Each twin ends up with two distinct cell populations of varying proportions.

References

{{Transfusion medicine Transfusion medicine