Hemizygous mice on a C57BL/6 background display increased pre-B cells in the bone marrow throughout life and a transient increase in large pre-B cells in the blood at 3-4 weeks of age. Spontaneous pre-B and B cell lymphomas reach an incidence of 50% at 15-20 weeks in hemizygous progeny of a wildtype female mated with a hemizygous male.

In conjuction with Tg(BCL2)22Wehi, transgenic mice on a C57BL/6 background exhibit the production of primitive lymphoid tumors within 5 weeks of birth