Abstract: The invention provides antibody to canine or feline or equine antigens. Specifically, antibodies directed to canine CD20 which have been caninized or felinized are provided. Also provided are methods for preparing high affinity antibodies to canine and feline CD20 as well as methods for treating B cell disorders in companion animals.

Abstract: The invention provides antibody to canine or feline or equine antigens, e.g., canine CDS2, and methods of making and using antibodies as described.

Abstract: The invention provides recombinant protein (e.g., a recombinant antibody or soluble receptor) having (i) a binding domain capable of specific binding to an epitope (for example an antibody variable domains, a receptor, a growth factor, a cytokine, or a fragment of any of the foregoing which is capable of specifically binding the desired epitope) and (ii) an effector domain comprising a constant domain region which is derived from immunoglobulin of a first species which is a companion mammal, e.g. dog, cat, or horse, having engineered substitutions at one or more positions and having an altered interaction with one or more FcRs or other ligands, and optionally enhanced effector function, relative to the parent constant domain region.

Abstract: The invention provides heterochimeric antibodies and/or fragments thereof comprising (i) hypervariable region sequences wholly or substantially corresponding to sequences found in antibodies from a donor species; (ii) constant region sequences wholly or substantially corresponding to sequences found in antibodies from a target species which is different from the donor species; and (iii) heavy and/or light chain variable framework sequences which contain at least three non-CDR residues corresponding to sequences found in antibodies from a target species and at least three contiguous non-CDR residues corresponding to sequences found in antibodies from a donor species. The invention further provides antibody to canine or feline or equine antigens, e.g., CD20 or CD52, and methods of making and using antibodies as described.