Disclosed herein are methods and compositions for enhancing the immunogenicity of a preselected protein or peptide antigen in a mammal. Immunogenicity is enhanced by fusing the preselected antigen to an immunoglobulin heavy chain constant region to produce an Fc-antigen fusion protein. The Fc-antigen fusion proteins bind Fc receptors on the surface of antigen presenting cells, thereby targeting the antigen to the antigen presenting cells in the mammal. In addition, disclosed is a family of adjuvants, for example, an Fc-adjuvant fusion protein, for use in combination with the Fc-antigen fusion proteins to enhance or modulate a particular immune response against the preselected antigen.