Hyperdiploid-CD5-positive B cells in mouse.

Hyperdiploid B cells have been found in autoimmune NZB mice as they age. The hyperdiploid cells were found to be clonal both on the basis of cytogenetic analysis and studies of immunoglobulin gene rearrangements at the DNA level. Studies of the inheritance of the hyperdiploid traits in both F1 and backcrosses, as well as NZB recombinant inbred strains, revealed that the presence of hyperdiploid B cells was an inherited recessive trait linked to autoimmune hyperactivity. In addition, hyperdiploid B cells were found to possess a unique chromosome pair which lacked terminal C-bands. This observation allowed analysis of the fate of transferred NZB hyperdiploid B cells into unirradiated recipients. The hyperdiploid B cells were found to expand in recipients and become the dominant population in several lymphoid organs. Spontaneously occurring hyperdiploid B cells were not observed in NZB-xid mice possessing the CBA/N X chromosome, which confers abnormal B cell maturation and results in decreased autoimmunity in NZB-xid mice. Following the discovery that CD5+ B cells were elevated in certain autoimmune states, hyperdiploid B cells were examined and found to be CD5+ B cells as well. The malignant cell in chronic lymphocytic leukemia is also a CD5+ B cell. The hyperdiploid B cells of NZB mice appear to have many of the features of autoimmune B cells, as well as malignant cells.