Microparticles with adsorbent surfaces, methods of making such microparticles, and uses thereof, are disclosed. The microparticles comprise a polymer, such as a poly(α-hydroxy acid), a polyhydroxy butyric acid, a polycaprolactone, a polyorthoester, a polyanhydride, and the like, and are formed using cationic, anionic, or nonionic detergents. The surface of the microparticles efficiently adsorb biologically active macromolecules, such as DNA, polypeptides, antigens, and adjuvants. Also provided are compositions of an oil droplet emulsion having a metabolizable oil and an emulsifying agent. Immunogenic compositions having an immunostimulating amount of an antigenic substance, and an immunostimulating amount of an adjuvant composition are also provided. Methods of stimulating an immune response, methods of immunizing a host animal against a viral, bacterial, or parasitic infection, and methods of increasing a Th1 immune response in a host animal by administering to the animal an immunogenic composition of the microparticles, and/or microemulsions of the invention, are also provided.