Histologic examination of normal skin demonstrates small numbers of perivascular cells, with darkly stained ovoid nuclei and granular cytoplasm on hematoxylin and eosin staining. The cells demonstrate metachromasia of the cytoplasm when stained with Giemsa stain. Which of the following products would these cells be most likely to secrete?

The cells in question are mast cells, which play an impoant role in IgE-mediated allergic responses. They are a normal (minor) constituent of dermal skin and are most definitely identified with stains, such as the Giemsa stain, that highlight the granularity of their cytoplasm (mast cells are closely related to blood basophils). Mast cells secrete histamine, serotonin, many leukotrienes, and platelet aggregating factor (PAF). Their histamine secretion after IgE stimulation helps to trigger the acute inflammatory pa of the allergic response. Bradykinin is a nonapeptide found in the plasma. It is a potent vasodilator and stimulates pain receptors. Complement factor 3a is a plasma protein that induces vascular leakage as pa of the acute inflammatory response. Interleukin 2 is secreted by lymphocytes and augments the immune response. Ref: Mescher A.L. (2013). Chapter 5. Connective Tissue. In A.L. Mescher (Ed),Junqueira's Basic Histology, 13e.