Crossreactivity between human and canine Ia antigens using a mouse monoclonal antibody (CIA)

A mouse monoclonal antibody (CIA) produced against human Ia antigens that reacts with 20-30% of human peripheral blood lymphocytes was found to react with more than 90% of dog lymphocytes. Less than 41% of the Ia-positive dog lymphocytes expressed surface immunoglobulins. Immunoprecipitation studies with 125I-labeled cells precipitated heavily labeled Ia bands at 28K and 35K from human cells, but from dog cells the 29K beta chain of Ia was much more heavily labeled than the alpha chain.