456 
HEMATOLOGY 
cytes which hemolyzed in the presence of anti- 
sera and complement, and subgroup A2 
included those dogs having group A erythrocytes 
which reacted with no hemolysis. Subgroup Ai 
cells were non-reactive in the presence of anti- 
Ao antiserum and complement. 
The system is the canine blood group responsi- 
ble for most observed transfusion reactions in 
dogs. In the dog the transfusion reaction is 
rarely of clinical significance since they usually 
occur only in a setting of previous sensitization, 
and when they do occur, although their clinical 
manifestations may seem severe, death rarely 
results. Recovery is usually rapid and complete. 
Transfusion reactions in dogs present some in- 
teresting parallels to severe hemolytic transfu- 
sion reactions in humans. 
In most cases a single transfusion of group A 
red cells into an unsensitized A negative dog 
will be tolerated without clinical manifesta- 
tions. Within a few days anti-A antibodies ap- 
pear in the serum of the recipient resulting in a 
shortened life span for the transfused A posi- 
tive cells. Since, in a clinical veterinary setting, 
it is rare for a dog to be multiply transfused, ini- 
tial isosensitization is usually not a problem 
and typing is often not undertaken in choosing 
donor blood. However, if the sensitized dog is 
transfused with type Ai red cells, a severe 
transfusion reaction may result characterized 
by chills, emesis, urinary and fecal incontinence, 
transient prostration, and fever beginning 
within a few minutes after the transfusion is 
initiated.51'53 Occasionally hives, asthmatic 
respirations, transient paresis of the hind 
limbs, and convulsions are seen either during or 
immediately after acute hemolytic reactions. 
Hemolysis, often severe, is usually a component 
of the reaction and is accompanied by hemo- 
globinuria and hemoglobinemia. The severe 
signs usually subside rapidly and the dog re- 
mains febrile and dehydrated for about 24 
hours, after which the animal returns to nor- 
mal. The renal function remains unimpaired, 
and, unlike the case in humans, histologic exam- 
ination of the kidneys reveals none of the stig- 
mata of acute tubular necrosis.^* An under- 
standing of the reasons for the absence of 
renal damage in the dog might increase our 
understanding of the genesis of acute renal 
failure in hemolytic transfusion reactions in hu- 
mans. 
Some of the elements involved in a transfusion 
reaction when Ai red cells were administered 
to a sensitized A negative dog are shown in the 
graphs (Figure 8). Before transfusion the re- 
cipient had an anti-A antibody titer of 1/256. 
The Ai erythrocytes infused were tagged with 
Cr^^ and the rate of in vivo hemolysis was de- 
termined in the recipient. Five minutes after 
administration of 20 ml of incompatible cells, 
no type Ai cells were detected in a sample of 
venous blood. Free hemoglobin was detectable 
in the plasma in 5 minutes and reached a maxi- 
mum at 20 minutes. These data suggest that the 
infused incompatible cells were sequestered 
out of the circulation before they were 
hemolyzed. ^5 Rapid transient thrombocyto- 
penia and leukopenia were also noted. No sig- 
nificant changes in serum antibody or comple- 
ment titers were observed. 
Hemolytic reactions also occur when serum 
from a dog sensitized to Ai erythrocytes is ad- 
ministered to a type A dog. Many of the same 
clinical signs are seen that are present when an 
A, sensitized A negative dog is infused with Ai 
erythrocytes. Hemolysis and hemoglobinuria 
are major features. The severity of the hemoly- 
tic reaction is directly proportional to the quan- 
tity of antibody administered. Five ml of serum 
containing a titer of 1/256 anti-A will produce 
measurable hemolysis in a type A dog. In con- 
trast to the hemolytic reaction resulting from 
infusion of incompatible cells to a sensitized 
dog, the period of hemolysis may extend over 
several days if the dose of antibody is large 
enough. The recipient's red cells react posi- 
tively in the antiglobulin test immediately after 
the antiserum is administered and may remain 
positive for several weeks. 
A hemorrhagic state is frequently encoun- 
tered as a component of the transfusion reac- 
tion in sensitized A negative dogs transfused 
with A positive blood and in A positive dogs^^ 
which receive serum containing anti-A-antibod- 
ies. Thrombocytopenia with impaired clot for- 
mation always accompanies the bleeding state. 
The thrombocytopenia apparently results not 
from immune lysis of platelets but rather from 
a sequestration of platelets out of the active cir- 
