CD11c.DTR mice develop a fatal fulminant myocarditis after local or systemic treatment with diphtheria toxin

Abstract

To assess the role of alveolar macrophages (AMs) during a pulmonary Aspergillus fumigatus infection AMs were depleted by intratracheal application of diphtheria toxin (DTX) to transgenic CD11c.DTR mice prior to fungal infection. Unexpectedly, all CD11c.DTR mice treated with DTX died within 4-5 days, whether being infected with A. fumigatus or not. Despite measurable impact of DTX on lung functional parameters, these constrictions could not explain the high mortality rate. Instead, DTX-treated CD11c.DTR animals developed fulminant myocarditis (FM) characterized by massive leukocyte infiltration and myocardial cell destruction, including central parts of the heart's stimulus transmission system. In fact, standard limb lead ECG recordings of diseased but not healthy mice showed a "Brugada"-like pattern with an abnormally high ST segment pointing to enhanced susceptibility for potential lethal arrhythmias. ). However, the key limitation of such systems is the absence of the cell subset under study for the entire life span, including the prenatal phase. This makes these animal models unusable for investigations where cells of interest have to be depleted at defined time points. To overcome these limitations conditional cell depletion strategies in which a defined cell population can be eliminated by chemical or physical treatment of the organism at any time point during an experimental procedure have been introduced [3][4][5].A widely used system of this type is the diphtheria toxin receptor-mediated conditional cell ablation in mice and rats [6,7]. Diphtheria toxin (DTX) is a two-subunit exotoxin secreted by Corynebacterium diphtheriae as virulence factor and binds to toxinsensitive cells via its receptor-binding domain. The host cell receptor for DTX is the heparin-binding EGF-like growth factor (HB-EGF), here termed diphtheria toxin receptor (DTR) [8]. Binding of DTX to DTR leads to rapid death of the DTR-expressing cell due to blockade of protein synthesis. DTR is expressed on many cell types and in different tissues [9,10] CD11c-LuciDTR mice and CD11c-DOG mice were both generated using the same bacterial artificial chromosome (BAC) in which the endogenous CD11c promoter is flanked by very large DNA sequences, likely to include many or all regulatory and enhancer elements. CD11c-LuciDTR mice and CD11c-DOG mice differ in the genes cloned under the CD11c promoter (DTR, Ovalbumin and eGFP for CD11c.DOG and eGFP, Cre recombinase, DTR, and luciferase for CD11c.LuciDTR). All three systems have been mainly used to characterize DC and also macrophage (M ) behavior in the context of different immunological questions. Among these models CD11c.DTR mice [7] have by far been used most extensively with >1000 studies relating to their use. We and others previously reported that CD11c.DTR mice treated systemically with DTX can develop adverse side effects and mortality and hence recommended the use of BM chimeras [16,17]. However, the reason for the morbidity that was observed 4-6 days after DTX treatment had not been elucidated...

Quantitative Analysis of Proteome Modulations in Alveolar Epithelial Type II Cells in Response to Pulmonary Aspergillus fumigatus Infection

“…The lung-resident immune system of healthy people effectively controls the growth of inhaled conidia. Under healthy conditions the lung respiratory surface is populated with alveolar macrophages (AM) that phagocytose conidia and serve as sentinel cells for the recruitment of neutrophil granulocytes (N) from the peripheral blood (6,7). N are extremely effective in phagocytosing conidia (8,9), which is the reason why especially lack or dysfunction of N is associated with a highly increased risk for IA development (10 -12).…”

Repopulating Kupffer Cells Originate Directly from Hematopoietic Stem Cells

“…A recent lineage-tracing study reported that Ly6C hi monocytes gave rise to repopulating KCs in liver-shielded BM-chimeras in which KCs depletion is triggered with diphtheria toxin (DT) administrations 8 . However, it is important to note that inflammatory response triggered by DT administration [28][29][30] can result in the recruitment of MOs, which can further differentiate into inflammatory macrophages in the liver 31 . Perhaps, that is why the number of Ly6C hi MOs increased in the initial stages of KC repopulation following DT depletion.…”

Depletion of CD11c⁺ Cells Does Not Influence Outcomes in Mice Subjected to Transient Middle Cerebral Artery Occlusion

“…Nevertheless, as there was not even a trend for a protective effect of DC depletion on day 3, it seems very unlikely that functionally relevant changes will arise afterwards. On the contrary, the functional status declined the longer the mice were treated with DTX, most likely due to development of myocarditis, which was described shortly after we finished our experiments [35] . Third, differences in DC markers between humans and rodents have been described, complicating the translation of preclinical data into the human situation [36] .…”