Approaches for Analyzing the Roles of Mast Cells and Their Proteases In Vivo

Abstract

The roles of mast cells in health and disease remain incompletely understood. While the evidence that mast cells are critical effector cells in IgE-dependent anaphylaxis and other acute IgE-mediated allergic reactions seems unassailable, studies employing various mice deficient in mast cells or mast cell-associated proteases have yielded divergent conclusions about the roles of mast cells or their proteases in certain other immunological responses. Such “controversial” results call into question the relative utility of various older versus newer approaches to ascertain the roles of mast cells and mast cell proteases in vivo. This review discusses how both older and more recent mouse models have been used to investigate the functions of mast cells and their proteases in health and disease. We particularly focus on settings in which divergent conclusions about the importance of mast cells and their proteases have been supported by studies that employed different models of mast cell or mast cell protease deficiency. We think that two major conclusions can be drawn from such findings: (1) no matter which models of mast cell or mast cell protease deficiency one employs, the conclusions drawn from the experiments always should take into account the potential limitations of the models (particularly abnormalities affecting cell types other than mast cells) and (2) even when analyzing a biological response using a single model of mast cell or mast cell protease deficiency, details of experimental design are critical in efforts to define those conditions under which important contributions of mast cells or their proteases can be identified.

Imaging protective mast cells in living mice during severe contact hypersensitivity

“…We proposed, based on experiments performed in mice with a profound MC deficiency related to abnormalities in Kit structure or expression (referred to herein as "Kit-mutant MC-deficient mice"), that MCs and MC production of IL-10 can limit skin pathology during severe contact hypersensitivity (CHS) reactions (6). As noted in that study, it has been appreciated for some time that Kit-mutant mice have several phenotypic abnormalities in addition to their MC deficiency, and subsequently we and others generated Kit-independent MC-deficient mouse strains that are deficient in MC populations due to genetic manipulations independent of alterations in Kit (7)(8)(9)(10)(11)(12).…”

Analyzing the Functions of Mast Cells <em>In Vivo</em> Using '<em>Mast Cell Knock-in</em>' Mice

“…Some of these mice also exhibit other phenotypic abnormalities beside their MC deficiency ( Table 1), and additional abnormalities might also be discovered as the phenotype of these newly described strains is still under investigation. All these mice and some additional new types of MC-deficient mice have been recently reviewed in detail 9,10,13 .…”

“…Finally, it should be noted that several strains allowing inducible depletion of MCs or Cre recombinase-mediated deletion of "floxed" genes in MCs have also been recently described 25,49,61 . These strains have been reviewed in detail elsewhere 9,10,13 and represent promising alternative -or complementary -approaches to study MC functions in vivo.…”

“…Numerous methodologies have been applied to study biological functions of MCs [9][10][11][12][13] . Many groups have focused on in vitro approaches using either cell lines (such as the human MC lines HMC1 14 or LAD2 15,16 ), in vitro derived MCs (such as human peripheral blood-derived MCs 17 , or mouse bone marrow-derived cultured MCs [BMCMCs] 18 , fetal skin-derived cultured MCs [FSCMCs] 19 and peritoneal cell-derived MCs [PCMCs] 20 ) or ex vivo isolated MCs from different anatomical sites.…”

“…More recently, several strains of mice with c-kit-independent constitutive MC deficiency have been reported [24][25][26] . All these mice and some additional new types of inducible MC-deficient mice have been recently reviewed in detail 9,10,13 .…”