Human
leukosialin is among the most abundant
sialoglycoproteins found on the surface of cells of the lympho-hematopoietic system.
Leukosialin, also known as
sialophorin, is involved in T cell proliferation, and its molecular
isoform changes upon cellular activation. We show that human
leukosialin is identical to the
antigens described by the
monoclonal antibodies (mAb) G10-2, G19-1 (CD43) and B1B6 (large
sialoglycoprotein). This identity was suggested by immunoblot analysis of transformed cell lysates. Further, fibroblasts transfected with the human
leukosialin cDNA gain reactivity to these mAb, showing conclusively that molecules recognized by these mAb are determined by the same
cDNA. Expression of the
leukosialin gene is readily detected on the surface of transfected human and mouse fibroblasts. Immunoblot analysis of the transfectants indicates that processing of the human
protein occurs in both species. Alterations of
leukosialin expression have been reported in patients with the
Wiskott-Aldrich Syndrome (WAS), an X-chromosome-linked immunodeficiency disease. While essentially all of the transfected
tumor and primary fibroblasts from normal individuals express the transfected gene on the cell surface, only half of the transfected Wiskott-Aldrich fibroblasts express CD43. Nonetheless, the antigenic pattern by immunoblot analysis of both normal and WAS-transfected fibroblasts appears identical. These results indicate that WAS-derived cells can express
leukosialin and that the product of WAS X-chromosome mutation may not be expressed in fibroblasts.