Provided is a Notch ligand protein or polypeptide comprising a Notch
ligand DSL domain; 1 to 5 (but no more than 5) Notch ligand EGF repeat
domains; optionally, all or part of a Notch ligand N-terminal domain; and
optionally, one or more heterologous amino acid sequences. Also provided
is a homogeneous or heterogeneous multimer of the protein or polypeptide
and a polynucleotide encoding the Notch ligand protein or polypeptide. An
immune response can be modified in a subject by administering the Notch
ligand protein or polypeptide to the subject.