Hetero ring-substituted oxoalkanoic acid derivatives having an immunity-controlling action and represented by the following general formula:
wherein R' represents a hydrogen atom, a lower alkyl group, or a phenyl, thienyl or furyl group optionally having in an optional position of the nucleus at least one substitutent of halogen, lower alkyl, lower alkoxy, mono- or di-lower alkylamino-substituted lower alkoxy, lower alkylthio, lower alkylsulfinyl, amino, nitro or cyano, R 2 and R 3 each represents a hydrogen atom or a lower alkyl group, A represents a lower alkylene group, X represents a sulfur atom or a vinylene group, Y represents a nitrogen atom or a methine group optionally having lower alkyl as a substituent, and Z represents a carbonyl group or a single bond.