The IgH 3' enhancer (normally located 170 kb from the promoter) with a floxed neo cassette was inserted downstream of the untranslated region. This insertion mimics the t(14;18) chromosomal translocation associated with human follicular B-cell lymphoma. Cre-mediated recombination removed the neo cassette. Protein expression is increased 3.5- to 5.5-fold.