A new antigen was reported in 2007 and found to be present in about 93% of U.S. dogs.7 It was temporarily named Dal because the index case involved a Dalmatian. The Dalmatian was typed as DEA 1.1, 3, 4, and 5 positive and DEA 7 negative
but became sensitized after multiple transfusions for chronic renal failure with blood typed as DEA 1.1, 4 positive only.
Because additional transfusions were necessary, compatibility testing was required. Major crossmatches between the index dog
and 55 non-Dalmatian donors that should have been compatible based on types DEA 1.1, 1.2, 3, 4, 5, and 7 were incompatible.
Major crossmatches between the index dog and only 20 of 25 (80%) unrelated Dalmatians were compatible. Incompatible transfusions
involving this antigen could result in acute and delayed hemolytic reactions. When transfusions become necessary for sensitized
Dalmatians, it appears that compatible donors will most likely be found within the Dalmatian breed.
Little is known about DEA 6 and 8 and about 11 other antigens thought to exist because typing sera for these antigens are
not available. Without typing sera for these antigens, their relationship to Dal could not be determined.
FELINE BLOOD TYPES AND ANTIBODIES
In cats, only the AB system has been routinely recognized and consists of three types: A, B, and AB.
Type A is the most common and occurs in more than 95% of domestic shorthaired and longhaired cats in the United States. To
date, all Siamese, Burmese, Tonkinese, Russian blue, American shorthair, and Oriental shorthair cats have been identified
as type A.8-10 Type B has been identified in up to 10% of Maine coon and Norwegian forest cats; up to 20% of Abyssinian, Birman, Persian,
Somali, Sphinx, and Scottish fold cats; and up to 45% of exotic and British shorthair, Cornish rex, and Devon rex cats. Type
AB has been observed in domestic shorthaired cats as well as in breeds with type B.11
This blood system follows simple Mendelian inheritance with the A (A) gene having dominance over the AB (ab) gene, which has
dominance over the B (b) gene. Type A cats may have any one of three genotypes: A-A, A-ab, or A-b. Type AB cats may have either
an ab-ab or ab-b genotype, and a type B cat can only have the b-b genotype. Thus, a breeding pair of type A cats can produce
kittens of types A, AB, or B, depending on their phenotypes.
Unlike dogs, cats have marked naturally occurring antibodies. All type B kittens develop antibodies within a few weeks after
birth, and high titers develop by three months of age.12 As a result, type B queens will have strong anti-A antibodies in their colostrum without any prior exposure from pregnancy
or transfusion. Type A kittens will also develop antibodies, but these are generally considered less potent. Since antibodies
can be transferred to a kitten through the colostrum for up to 16 hours after birth, kittens born healthy can suddenly fade
from the hemolytic anemia that develops. This hemolytic anemia generally occurs in type A or AB kittens born to B queens mated
with type A toms.13
Type AB cats are considered to be universal recipients since they lack anti-A and anti-B antibodies; however, they should
be transfused with type A cells to avoid inadvertently transfusing potent anti-A antibodies from a type B donor, which is
an example of a minor side reaction. Because of the effects of geography and breed on the frequency of blood types, the risk
of inducing a potentially fatal transfusion reaction in type B recipients could be as high as 20% when transfusing unmatched
A new antigen, Mik, was reported in 2007 and is present in many domestic shorthaired cats.14 Cats lacking this antigen (about 6% of those tested) have the potential to develop an acute hemolytic reaction after the
transfusion of AB matched blood. Since typing serum is not available for the Mik antigen and antibodies appear to be naturally
occurring, crossmatching even type-matched cats before a transfusion is prudent.