PURPOSE: To obtain a reg gene to be coded with reg gene, by forming a gene to hybridize with a prove comprising the whole or part of a base sequence to code a specific amino acid sequence and to be manifested by a mammal spleen.

CONSTITUTION: When reg protein which is coded by reg gene contains a saccharide chain, an eucaryote of yeast or monkey cell is preferably used as a host. For example, when yeast is used, a well-known vector such as pGPD-1 is usable. When money cell COS is used, an expression vector such as pKSV-10 is usable. The expressed human reg protein can be purified according to a conventional purifying method by a proper combination of centrifugal separation, chromatography, dialysis and salting-out.