Abstract
This paper reviews the application of flow cytometric techniques to the analysis and quantitation of mixed red cell populations. Such mixtures may arise in a variety of ways, for example: through transplacental hemorrhage during pregnancy or upon delivery; through iatrogenic procedures such as blood transfusion, bone marrow or peripheral blood stem cell transplantation; or through disease, when a loss of surface antigen expression may occur due to the expansion of abnormal progenitors lacking the appropriate gene or lacking the ability to translate the product of the gene. Flow cytometry can offer a simple and accurate means of identifying and quantitating mixed red cell populations through detection of antigens specific for either donor or recipient, and in many cases it is possible to distinguish homo- or heterozygous expression of a common antigen. Internal antigens may be accessed after fixation and permeabilisation of the red cells. These latter techniques are relatively new and expand the spectrum of antigenic differences available for the identification of individual species in mixed populations.