Apical and basal Forssman antigen in MDCK II cells: a morphological and quantitative study.

We have studied the surface distribution of a glycosphingolipid (the Forssman antigen) in MDCK II and CCL39 cells. The Forssman antigen is mobile on the surface of both these cell lines. Its surface distribution is homogenous on non-polarized cells. Under conditions where MDCK II cells are well polarized, the Forssman antigen is present in equal amounts on the apical membrane and on the basal membrane and its processes. Very little Forssman antigen can be detected on the lateral membrane. The nature of the mechanism excluding the Forssman antigen from the lateral domain remains to be determined. This surface distribution is established within hours after plating and was observed with cells grown on different types of filters. The surface density of the Forssman antigen on the apical and on the basal domain has been estimated. No involvement of the basal Forssman antigen in cell attachment could be demonstrated. However, the apical Forssman antigen appears to be essential to the establishment of the cells in culture.