Mast cells

There is good evidence for mast cell heterogeneity both in the rat model and in the human. The rat and human differ substantially in the characteristics of mast cells found in various tissues and in their functional properties. The human situation is apparently more complex than the relatively simple definitions of CTMC and IMMC available in the rat. Some of the differences between tissues may be explained by mixture of cell types within a given location and by the effects of isolation procedures. The recognition that mast cells interact with the nervous system, by whatever mechanism, allows for CNS influence on mast cell activity. The often-quoted psychological component of diseases such as "food allergy", IBD and IBS could have a functional basis via mast cell activation. The potential role for mast cells in altering gut motility may also be important in this context. To date most of the work on mast cell-nerve interactions has considered the IMMC. Whether similar communication exists between CTMC and the nervous system remains to be elucidated. The recent observations of cytokine production by mast cells opens up an entirely new set of questions in mast cell biology. The importance of mast cells in immunoregulation and their potential for providing what have traditionally been thought of as T cell-derived factors may prove to be of great importance. This aspect of mast cell activity has not yet been examined with regard to mast cell heterogeneity. Given the differences in mast cell types with respect to other parameters, it would not be surprising if cytokine production was different in CTMC and IMMC populations. These areas and the issues still to be answered regarding the lineage and regulation of mast cells in different tissues provide major questions for future research.