BALB/c strain mice are unique in that they develop murine plasmacytoma (MPC) as a consequence of the inflammation induced by pristane oil injection in the peritoneal cavity. In this work the Treg, Th17, B1, B2, and NHC lymphocyte populations from the peritoneal environment of BALB/c, the susceptible strain, and C57BL/6 mice, which do not develop MPC after oil treatment, were studied. Both oil-treated strains showed decreased levels of Th17 lymphocytes, no significant variation in Treg lymphocytes, and a drastic decrease of all B lymphocyte populations. However, only oil-induced BALB/c showed increased levels of natural helper cells (NHC) which could be important in the myeloma induction.