Abstract: A biologic response modifier is described for human or animal treatment. It comprises natural membrane vesicles and ribosomes in a suspending buffer. The membrane vesicles are comprised of cellular membrane material endogenous to a selected microorganism. The ribosomes are also endogenous to the selected microorganism. The biologic response modifier is substantially free of endotoxin, intact cells, cell walls, and cell membrane fragments. The selected microorganism is one which does not evoke a significant immune deviating response in the patient and is an organism which is substantially non-pathogenic in humans. The selected microorganism is also one in which membrane vesicles are capable of being formed from cell membrane material and which are readily endocytosed by the monocyte-macrophage cell line of the patient.