Monoclonal antibodies to tissue-restricted autoantigens in the mouse epidermis

The humoral response to allogeneic epidermal cells (EC) in the mouse is dominated by the response to autoantigens. To investigate this phenomenon, several hybridoma clones that secrete monoclonal antibodies (MoAbs) that reacted specifically with EC were isolated. Three of these MoAbs--A3.1-6, A4.1-2 and A4.2-5--were further characterized. Competitive blocking assays were utilized to show that A4.1-2 and A4.2-5 recognize the same or closely associated determinants and that A3.1-6 recognizes a unique determinant. MoAb A3.1-6 reacts equally well with mouse and human EC; A4.2-5 shows little, if any, reactivity with human EC. In immunofluorescence assays of mouse skin, A3.1-6 stained the perinuclear cytoplasm of keratinocytes in most, if not all, layers of the epidermis whereas A4.2-5 strongly stained an extracellular antigen expressed in the middle cell layers. Immunoblot analysis showed that the target antigen of A3.1-6 is a keratin polypeptide of approximately 55 kd.