Skn antigens: identification of a 95-kilodalton protein in mouse neural tissue

Skn alloantigens represent a tissue-specific histoincompatibility system based on their expression in epidermal cells and absence in hematopoietic tissue. Radiation chimeras produced by lethally irradiating C57BL/6 mice and reconstituting them with (C57BL/6xA/J)F1 spleen cells reject skin from A/J (A) or (B6xA)F1 donors. The studies reported here were designed to determine the expression of the Skn 2.1 alloantigen on neural tissue given the common ectodermal origin of epidermal and neuronal cells. Using a monoclonal antibody specific for the Skn 2.1 alloantigen, a protein of 95 kilodaltons was identified in brain cells of A mice and, by immunohistochemical staining, Skn 2.1 was found in neurons in the brain. Although the antigen was detected in the cerebral cortex, cerebellum, and hippocampus of the brain, the staining of cells within these regions was not uniform. Because there is a restricted pattern of Skn 2.1 expression, limited to cells of ectodermal lineage, it is hypothesized that Skn may play a role in the differentiation of ectodermally-derived tissues.