Chromosomal abnormalities in spleens of New Zealand black mice, a strain characterized by autoimmunity and malignancy.

Mosaicism of normal and chromosomally aberrant cells was detected in 14 of 20 spleens from adult New Zealand Black (NZB) mice reared under conventional conditions, a strain that spontaneously develops autoimmunity and lymphoreticular malignancy. No abnormalities were found in marrows from these same animals or in spleens from NZB mice younger than 3 months. The prevalence of chromosomal aberrations was significantly higher in spleens from NZB mice than in spleens from the two other strains studied-SJL/J, which has high frequency of reticulum cell neoplasia and paraproteinemia but no autoimmunity, and BALB/c, which has essentially no autoimmunity and only a low incidence of generalized lymphoid neoplasms and plasmacytomas in ageing animals. Causes for the chromosomal abnormalities in NZB mice are considered in terms of other features in these mice-immunoproliferation, autoimmunity, and the presence of murine leukemia ("C"-type) virus particles.