an immunological response potentiation process is disclosed for synthetic or genetically engineered antigens having low immunogenicity . the antigen is embedded into biodegradable microparticles , these antigen - loaded microparticles are dispersed in a biodegradable medium which triggers when it is parenterally administered a potentiated antibody , t h - lymphocyte and t c - lymphocyte response , as compared to an aqueous antigen solution . the extent of immunological potentiation is at least comparable with that attained by ifa compositions . linear b - t h - cell epitopes , linear t c - cell epitopes , dimers and multimers of said epitopes , as well as their mixtures , are used as low immunogenicity antigens . the microparticles are based on biodegradable biopolymers such as polyester , polyanhydride , polyorthoester . by mixing microparticles with different wettabilities , swellabilities , release and biodegradation times , the most intense and longest immunological potentiation is achieved . this process is useful for immunising human beings and animals against diseases caused by viruses , bacteria , protozoa or tumour cells .