Figure 2.

IgE (allergic) vs. non-IgE (pseudoallergic)-mediated activation of mast cells. Mast cells can be activated either through an IgE or non-IgE pathways. IgE stimulation requires pre-exposure to an antigen (e.g., pollen, mite, etc.) and upon a 2nd exposure, IgE-bound FcεR1 are crosslinked leading to activation of signal transduction pathways that culminate in cell degranulation and activation (Top panel). Mast cells can be also activated through non-IgE pathways by a wide range of materials (e.g., cytokines, complement fragments, basic polypeptides, environmental toxicants, toxic venoms, etc) which don't require prior exposure and may lead to mast cell degranulation and/or activation (Bottom panel). The underlying molecular mechanisms of non-IgE-mediated mast cell degranulation and activation are largely unknown.