Mice that are homozygous for the transgene are viable, normal in size and do not display any gross physical or behavioral abnormalities. These transgenic mice have a diphtheria toxin (DT) inducible system that transiently depletes macrophages in various tissues. The transgene insert 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). RT-PCR analysis of bone marrow macrophages detects specific transgene expression. Cytological analysis of thioglycollate treated peritoneal cells shows the absence of macrophages. Intraperitoneal injection of DT ablates monocyte/macrophage cells in the peritoneal cavity. Macrophage populations within various tissues demonstrate differential susceptibility DT induced deletion. Following DT administration macrophages are ablated in the peritoneum, kidney and ovary. Macrophage population is restored by day 4 following a single intraperitoneal dose of DT. Hepatic sinusoidal and alveolar macrophages were unaffected by administration of DT, and despite polymorphonuclear (PMN) leukocyte expression of CD11b, DT did not induce the death of recruited or circulating PMNs. This mutant mouse strain may be useful in studies of the specific role of macrophages in the immune response. Of note, when DT was administered at The Jackson Laboratory (Feb, 2010), splenic macrophages were still present, as assessed by F4/80 and CD11b staining. Higher doses (greater than 25ng/g body weight) of DT sickens the mice. Transgene expression is not sufficient to be detected by FACS analysis. In an attempt to offer alleles on well-characterized or multiple genetic backgrounds, alleles are frequently moved to a genetic background different from that on which an allele was first characterized. It should be noted that the phenotype could vary from that originally described. We will modify the strain description if necessary as published results become available. &nbsp;

These transgenic mice have a diphtheria toxin (DT) inducible system that transiently depletes macrophages in various tissues. The transgene insert 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). This mutant mouse strain may be useful in studies of the specific role of macrophages in the immune response.

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