Immunohistochemistry of human cutaneous Meissner and pacinian corpuscles

This paper reviews the immunohistochemical characteristics of two kinds of human cutaneous sensory nerve formations (SNFs), the Meissner and Pacinian corpuscles. In both kinds of SNF the central axon might be easily identifiable because it displays immunoreactivity (IR) for the neuroendocrine markers neuron-specific enolase and protein gene product 9.5, as well as for neuron-specific intermediate filament proteins, i.e., neurofilaments. Other intermediate filament proteins such as vimentin are localized in the lamellar cells of Meissner corpuscles, and in the inner core, outer core and capsule of Pacinian corpuscles. However, they lack cytokeratins or glial fibrillary acidic protein IR. On the other hand, and in agreement with ultrastructural data, IR for basement membrane constituents laminin and type IV collagen is found underlying all SNF constituents, with the exception of the axon. One of the mechanisms involved in the maintenance of intracellular calcium ions (Ca2+) homeostasis is the calcium binding proteins. Ca2+ play a key role in the mechanoelectric transduction and have been localized in SNFs. In this way IR for the Ca(2+)-binding proteins calbindin D28K, parvalbumin and calretinin, is present and colocalized in both Meissner and Pacinian corpuscles; furthermore, S-100 protein is exclusively localized in the lamellar cells and the inner core. On the other hand, the skin is a main source of neurotrophins for a subset of neural crest sensory neurons, some of which end forming SNF. These factors are conveyed via retrograde axonal transport from the skin to the cell body of the responsive neurons. Interestingly, Meissner and Pacinian corpuscles also display IR for the pan-neurotrophin low-affinity receptor (p75), and for the trkA receptor protein, a basic constituent of the high-affinity receptor for some neurotrophins. Moreover, they express IR for the epidermal growth factor receptor. Finally, other antigens not proper to the cells forming human cutaneous SNF, such as the epithelial membrane antigen and the leucocytary antigen-7, have also been detected.