Download Group_4_Abstract - Mast Cell

COST Action BM1007 Mast Cells and Basophils – Targets for Innovative Therapies
2nd Training School
The Search for Mast Cell and Basophil Models – Are We Getting Closer to Pathophysiological
Relevance?
January 20-21, 2014 – Jerusalem, Israel
Abstract Group 4 Mast cell deficient mouse models
Trainer: Francesca Levi-Schaffer
Trainees: Yu Fang, Hans Juergen Hoffmann, Ofir Klein, Desiree Ludwig, Carolin Sieber
In the field of mast cell and basophil research, the most used experimental tools are based on
murine models. Regarding basophils not much research on animal models has been carried out as
yet. In general, we can distinguish between two types of mast cell deficient mouse models: c-Kitdependent models and c-Kit-independent models. Until recently the c-Kit dependent models were
the most commonly. However, these models have been shown to be not only depleting mast cells,
but also impair many other immune cells thus possibly affect a broad range of physiological
mechanisms. Therefore, new mouse models have been created that do not depend on c-Kit
mutations in order to avoid a broad effect on other immune cells. In our presentation we focus on
three different mast cell deficient mouse models and a basophil deficient mouse model.
C57BL/6-Kitw-sh / C.B6-Kit w-sh mouse model
For many years, the mouse models used for allergy research were mouse exhibiting a
pronounced Th1 phenotype (C57Bl). However, human allergic reaction exhibits a pronounced Th2
phenotype. In order to better understand the human allergic reaction, Becker et al. generated a
BALB/c mouse carrying the Kitw-sh inversion mutation, termed C.B6 w-sh. Surprisingly, while C.B6 w-sh
do not develop a passive cutaneous reaction in the ear, the C.B6 w-sh mouse develop airway
hypersensitivity response in the absence of mast cells, and in contrast to the common model mouse
– C57BL/6-Kitw-sh.
Mas-TRECK and Bas-TRECK mouse model
Another newly established mast cell-deficient mouse model is the Mas-TRECK and Bas-TRECK
mouse, based on Diphtheria toxin (DT) conditional deletion system using IL4 enhancer elements
previously shown to be specific for IL-4 transcription in mast cells or basophils. DT treatment of
Bas-TRECK mice resulted in specific deletion of basophils, whereas both mast cells and basophils
were deleted in Mas-TRECK mice. These selectively conditional mast cell or basophil depletion
models enable the researchers to better distinguish the role of mast cells and basophils in several
pathological processes induced by IgE, including passive cutaneous anaphylaxis (PCA) and systemic
anaphylaxis, and also in a non-adjuvant-induced chronic asthma model. Results generated from this
model clearly show that mast cells are responsible for the immediate type I allergic response that
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may lead to anaphylaxis, while basophils play a role in the late phase response. Mast cells but not
basophils are involved in development of chronic airway hypersensitivity.
Cre-Master mouse model
The Cre-Master mouse model is a mast cell deficient mouse model based on Cre mediated
genotoxicity. By expression of Cre under the mast cell specific Cpa3 promoter, mast cells undergo
apoptosis when they start to express Cpa3. This model does not depend on c-kit dependent
mutations or on the injection of DT toxin. So far there is only a minor reduction of basophils
observed and no other described defects of other immune cells by the Cpa-dependent Cre deletion
mechanism in these mice. Therefore this is an excellent model for a constitutive deletion model of
mast cells.
Conclusion
During the last years several new mouse models have been created that to not dependent on c-kit
mutations and therefore offer a more regulated deletion of mast cells. Not only constitutive but also
inducible mouse models for mast cell deficiency are now available to allow detailed analysis of mast
cell functions in vivo. Although these models exhibit less off target changes in the immune system
compared to c-kit dependent models there are still differences especially concerning the number of
basophils. It is worthwhile to analyse better this model to ensure that the model is only mast cell
deficient and does not affect other cells like innate lymphoid cells or other innate immune cells
involved in Th-2 and other responses. Also the influence of the microbiota should be addressed in
these mice. Moreover the induction of apoptosis of mast cells within the tissue may also influence
the outcome of the results. Not all disease models are transferable from human to mouse. Therefore
the use of humanized mouse models or the expansion of human experimentation should also be
considered.
To sum up for every experimental setup the possibility of either using an inducible or constitutive
mast cell deficient mouse model as well as the number and role of basophils and additional cells
that may influence your settings should be considered. Not only the mast cell deficient mouse
model should be carefully chosen but also the disease model and the experimental set up should be
appropriate to the experimental question.
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