Alloantibodies against A and B blood types in cats.

This study characterizes the naturally occurring feline alloantibodies against A and B blood type. All examined type-A and type-B cats had naturally occurring antibodies against erythrocytes of the opposite blood type. In order to determine the class of immunoglobulins, sera from cats were analyzed using incubation with 2-mercaptoethanol (2-ME), immunoprecipitation, and gel filtration. Type-A cats had weak agglutinins of the IgM class and weak hemolysins which consisted of approximately equal parts of IgG and IgM class. Type-B cats had strong hemagglutinins and hemolysins mostly of the IgM class. Colostral antibodies were detectable in newborns as early as 4 h after birth and their own alloantibody production started at 6-8 weeks of age. The presence of naturally occurring alloantibodies, in particular the anti-A alloantibodies, renders cats susceptible to clinical incompatibility reactions.