Trends in Immunology
ReviewThe role of mast cells in host defense and their subversion by bacterial pathogens
Section snippets
MC types and culture conditions
Before discussing specific results, it is pertinent to review the different types of MC and discuss which types are used typically for studies involving microorganisms. To date, most studies have used pure populations of rodent or human cultured MCs and have shown that their responses are, for the most part, comparable [10]. Rodent MCs are heterogeneous and are categorized as either mucosal-type or connective-tissue-type, based on their tissue locations, staining patterns, content of proteases
MCs have clear protective roles during bacterial infections
Several recent reports in the literature indicate that MCs can mediate a variety of antimicrobial activities. Although some of these antimicrobial functions are similar to those reported for the primary effector cells of the innate immune system, MCs possess certain unique features that make their functions particularly crucial for host defense: (1) MCs are located strategically at the host–environment interface, such that they are one of the first types of inflammatory cell to encounter the
MCs might have deleterious effects during bacterial infections
The appropriate release of mediators by MCs challenged with microbes has clear protective effects for the host, as shown by the in vivo studies described above [44]. Nevertheless, the intrinsic capacity of MCs to induce marked pathological effects by the excessive or inappropriate release of inflammatory mediators might be significant in many infectious situations. There is a growing realization that successful pathogens not only evade or resist the host's inflammatory response but can also
Concluding remarks
There is ample evidence now pointing to a multifaceted and central role for MCs in the host's immune response to bacterial pathogens. MCs are capable of rapid reaction to a wide range of bacteria. The MC responses involve the ingestion and killing of adherent bacteria and a measured mediator response, which is crucial for the early influx of neutrophils to sites of bacterial infection. MCs might contribute also to the processing and presentation of bacterial antigens to immune cells. These
Acknowledgements
We would like to express our appreciation to AMGEN Inc. (Thousand Oaks, CA, USA) and Novartis Biotechnology (Basel, Switzerland) for their continuous and generous help. We also thank Viviane Tricottet for expert advice concerning electron microscopy, and Nadine Ben Hamouda, René Lai-Kuen and Laurence Leriche for expert technical assistance. This work was supported in part by research grants from the NIH (AI 35678 and DK 50814) and ARC (ARC 5203).
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