It has also been reported that direct exposure of human peripheral blood mast cells to a Lactobacillus rhamnosus strain lead to a downregulation of FceR1 expression on the cell surface. We did not assess FceR1 expression on mast cells from JB-1 fed animals. However, as treatment with JB-1 also inhibits degranulation in response to non-IgE mediated activation it is unlikely that a changes in expression of this receptor account for the inhibition of degranulation observed. Overall, these results suggest that inhibition of mast cell responses may be a component of the systemic immunomodulatory effects of commensal bacteria and a contributing factor to the ability of certain candidate probiotic organisms to attenuate allergic inflammation. Future studies will focus on potential mediators and corresponding receptors responsible for mast cell stabilization. The KCa3.1 PI-103 channel current has been identified as critical to the function of many immune cells and has been proposed as a therapeutic target in a range of immune disorders including allergy. Thus it will be interesting to determine if the channel’s function is altered in other cell types and whether inhibition of KCa3.1 may contribute to a number of the diverse physiological effects described for certain commensal organisms. They modulate numerous physiological processes in excitable and non-excitable tissues and take part in forming macromolecular signaling complexes. The protein encoded by KCNMA1 represents the pore-forming a subunit of the a-subunit of the large conductance, voltage and Ca2+ activated K+ channel. The a-subunit can form macromolecular complexes with four different types of auxillary b-subunits and local Ca2+ influx channels. Because of the large number of protein interactions and activating factors influencing BK channel function, including intracellular Ca2+, membrane voltage, pH, shear stress, carbon monoxide, phosphorylation states, as well as G-proteins and steroid hormones, it is generally difficult to predict the role of BK channels in a given tissue. Moreover, phosphatidylinositol 4,5-bisphosphate, PI3K and PTEN can regulate BK channel activity. Finally, BK channel function and pharmacological properties are fine-tuned by differential splicing and depend on the presence of auxiliary b-subunits. In many diseases, defective regulation/or expression of BK channels have repeatedly been associated with altered cell cycle progression, cell proliferation, and cell migration. These factors are fundamental to the development of cancer. As demonstrated in electrophysiological studies on cervical and breast cancer cells, BK channels are directly activated by estrogens, which have an essential role in cancers of the uterus, breast and prostate. Early reports pointed to high levels of KCNMA1-expression in human glioblastomas. A number of subsequent reports pointed to a more general role of BK channels in different types of cancer, although this not seems to apply to all. We previously detected genomic amplification of the BK channel encoding gene KCNMA1 in 16% of late-stage prostate cancers, identifying KCNMA1 as one of the most common amplifications in prostate cancer. We found that knockdown of KCNMA1 by siRNA and specific BK channel blockade by iberiotoxin inhibited cell proliferation of the prostate cancer cell line PC3, which carries an amplification of KCNMA1. This study suggested a specific role of KCNMA1 in the transition from hormone-sensitive to hormone-insensitive and castration-refractory prostate cancer. Our study reveals for the first time that KCNMA1 amplification is restricted to human cancer types that derive from tissues regulated by sex steroid.