The goals of this session are to provide some information related to blood types, blood typing, crossmatching, and to relate
a few case examples that emphasize the usefulness of knowing what you may be working with. The focus will be on dogs and cats,
but horses will be discussed as well.
Blood types are classifications of heritable species-specific antigens comprised of proteins, lipids, and/or carbohydrates
(glycolipids, glycoproteins). Other cells, as leukocytes, platelets or other tissues may also share these antigens. Rarely,
antigens are shared between species. Alloantibodies (or isoantibodies) are antibodies present in the serum against an antigen
from another animal of the same species. These may be naturally acquired or induced through previous exposure as with transfusion.
Canine blood types and antibodies
Dog blood types are known as the Dog Erythrocyte Antigen System (DEA) and are numbered. DEA 1 was formerly known as "A" and
consists of 4 alleles: negative, 1.1, 1.2, and 1.3. DEA 1.1 and DEA 1.2 are the most important antigens and together comprise
approximately 60% of the canine population. Both of these types are considered "A positive", however type DEA 1.2 dogs, which
comprise 7-29% of the canine population, will develop potent anti-DEA1.1 antibodies once transfused with DEA 1.1 cells. Naturally
occurring antibodies to these antigens are generally considered nonexistent. First time transfusions may be associated with
a decreased circulating lifespan of the transfused cells and subsequent transfusions will be associated with an acute hemolytic
reaction. DEA 1.3 is only known to exist in German shepherd dogs from Australia.
DEA 4 comprises up to 98% of the general dog population but only ~75% in Doberman Pinschers. Dogs with this type alone are
considered "universal donors". Naturally occurring DEA 4 antibodies are not known to exist. DEA 3 and 5 are expressed in
lesser proportions of the dog population, but greyhounds tend to have upwards of 23% and 30% of DEA 3 and 5, respectively.
DEA 7 is present in 8-45% of the population. Naturally occurring antibodies have been observed against these antigens with
a delayed transfusion reaction causing decreased lifespan of transfused cells but no hemolysis. Dal is a high frequency antigen
reported in 2007 that is lacking in ~20% of dalmations tested (5/25). IgG antibodies apparently developed by 40 days after
transfusion; 55 non-dalmation donors were all incompatible at this time. Incompatible transfusions involving this antigen
could result in acute and delayed hemolytic reactions. Little is known about DEA 6, 8 and ~11 other antigens thought to exist.
Typing sera for these antigens are not available.
Cat blood types and antibodies
Only the "AB" system in cats has been routinely recognized to date and consists of three types: A, B, and AB. Type A is the
most common and comprises over 95% of the general domestic shorthair/longhair population in the United States. Type B is
more common in certain breeds: up to 10% of Maine coon and Norwegian Forest; up to 20% of Abyssinian, Birman, Persian, Somali,
Sphinx, and Scottish Fold; and up to 45% of Exotic and British Shorthair, Cornish Rex and Devon Rex. It has not been observed
to date in Siamese, Burmese, Tonkinese, Russian Blue, American Shorthair and Oriental Shorthair.
Type AB has been observed in the domestic shorthair as well as breeds known to have Type B. 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 phenotypes: A-A, A-ab, or A-b. Type AB cats may have either ab-ab or ab-b phenotypes,
and a type B cat can only have the b-b phenotype. Therefore, a breeding pair of Type "A" cats can produce kittens of Types
A, AB or B, depending on their phenotypes.
Cats have naturally occurring antibodies. All type B kittens develop antibodies within a few weeks after birth and high titers
develops around three months of age. Type A kittens will also develop antibodies, but these are generally considered less
potent. Since antibody can be transferred to the kitten via the colostrum up to 16 hours after birth, kittens born healthy
can suddenly "fade" from the hemolytic anemia that develops. This generally occurs in type A or AB kittens born to B queens.
Type AB cats are considered to be universal recipients as they will 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. This would
be an example of a "minor-side" reaction (see minor crossmatch info below)..
A new antigen, "Mik",was reported in 2007 and is present in a high number of DSH cats. Those lacking the antigen (~6% of those
tested) have the potential to develop an acute hemolytic reaction after transfusion of AB matched blood. This emphasizes
the importance of crossmatching all cats prior to transfusion.