The Cartwright blood group system (ISBT 011) is also known as the YT blood group system and contains two antithetical antigens, Yta and Ytb, with Yta expressing on 99.8% of all red cells and Ytb expressing on less than 1% of red cells. They were first discovered in 1956 and named after a patient who produced the first known anti-Yta, Mrs. Cartwright.
Disease Association
These antigens are located on the acetylcholinesterase (AChE) protein, which is involved in neurotransmitter function. Reduced levels of AChE is associated with myelodysplasias and some cases of SLE. And like JMH antigens, PNH III RBCs lack YT antigens with no known link between the cause of the disease and the absence of antigen expression. The function of YT antigens on RBCs is also not known.
These antigens differ from those previously discussed in this course as they are considered immunogenic and the antibodies are clinically significant. Anti-Yta often takes on the appearance of an "HTLA" antibody but is a mimic rather than a true "HTLA" antibody.
Treatment
YT antigens are sensitive to pronase and disulfide bond-reducing agents, have variable reactions with enzymes and trypsin/alpha-chymotrypsin, and will also readily adsorb out of the plasma, which can aid in antibody identification if there are no RBCs lacking the Yta antigen available.
Common Findings
In the case of a patient with an anti-Yta, it is recommended to determine the clinical significance before transfusion using a Monocyte Monolayer Assay (MMA) since antigen-negative blood is extremely rare.
