Pyridine derivatives represented by the following general formula
wherein R 1 , R 2 , R3, and R 4 , which may the same or different, each represents a hydrogen atom or a lower alkyl group, or R 1 and R 2 , or R 3 and R 4 , are taken together to form a hetero ring together with the adjacent nitrogen atom, A 1 and A 2 , which may be the same or different, each represents an alkylene or hydroxy-substituted alkylene group, Y' and Y 2 , which may be the same or different, each represents an oxygen or sulfur atom, and Z represents
or the pharmaceutically acceptable acid addition salts thereof. These compounds show pharmacological effects such as acceleration of leukocyte phagocytosis, acceleration of macrophage phagocytosis, acceleration of production of rosette forming cells of spleen, and depression of adjuvant arthritis, thus being useful as medicines.