Second, the therapeutic differentiation antigen may be a mutant form of a syngeneic differentiation antigen, for example a glycosylation mutant.

For example, a mouse differentiation antigen can be used to stimulate an immune response to the corresponding differentiation antigen in a human subject.

Both of these monoclonal antibodies react with a previously unrecognised human leucocyte differentiation antigen.

Tolerance of the immune system for self-differentiation antigens can be overcome and an immune response stimulated by administration of a therapeutic differentiation antigen.

Third, the therapeutic differentiation antigen may be a differentiation antigen (wild-type or mutant) of the same type from a species different from the individual being treated.