EXPRESSION OF CD15 IN A SUBSET OF DORSAL-ROOT GANGLION-CELLS DURING THE CHICK EMBRYONIC-DEVELOPMENT

We have investigated the distribution of CD15 immunoreactivity (IR) in chick sensory neurons during the embryonic development. IR first appe ared around embryonic day 6 (E 6) preferentially in the lateroventral part of the dorsal root ganglion (drg). Here it was located in the cyt oplasm of the ganglion cells. Starting at E11, CD15 positive cells hav e been detected also in the dorsomedial part of the drg. Towards the e nd of embryonic development, these immunoreactive (ir) cells were even ly distributed within the drg. Around E 16 nerve fibres could also be found, expressing the CD15 epitope. These fibres run both in centripet al and centrifugal direction, and could be followed throughout periphe ral nerves. IR was confined to peripheral nerves of the skin, where af ter its subepidermal arborisation fine nerve terminals entered the bas al stratum of the epidermis or the dermal bulbous part of feathers. Un til hatching no staining in visceral structures was detected. Our resu lts suggest that CD15 is restricted to a subset of drg neurons innerva ting somatosensory targets. A role for the CD15 epitope for myelinatio n is discussed.