The transgene contains a fusion product involving simian diphtheria toxin receptor and green fluorescent protein under the control of the human ITGAM (integrin alpha M) promoter (CD11b), and human growth hormone sequence. Mice carrying this transgene have a diphtheria toxin (DT) inducible system that transiently depletes macrophages. RT-PCR analysis of bone marrow macrophages detects specific transgene expression.