IMMUNOFLUORESCENCE AND IMMUNOELECTRON MICROSCOPY ANALYSES OF A HUMAN MONOCLONAL ANTIEPITHELIAL CELL-SURFACE ANTIBODY THAT RECOGNIZES A 185-KD POLYPEPTIDE - A COMPONENT OF THE PARANEOPLASTIC PEMPHIGUS ANTIGEN COMPLEX

We recently reported the production of a human monoclonal antibody (Mo Ab) derived from a patient with pemphigus vulgaris (PV) that binds to the keratinocyte membrane and reacts with a 185-kD polypeptide by immu noblot analysis. We have since examined the tissue specificity of that MoAb, F12. By indirect immunofluorescence (IIF), F12 stained both the cell membrane and the basement membrane zone of stratified squamous e pithelia. Moreover, MoAb F12 stained other epithelial tissues, such as urinary bladder, small bowel, thymus, and liver, and non-epithelial t issues, such as myocardium. indirect immunoelectron microscopy (IIEM) analysis showed that MoAb F12 bound to a component common to desmosoma l and hemidesmosomal plaques and to zona adherens-type junctions betwe en hepatocytes and bile duct cells. Inhibition experiments were then p erformed with sera from patients with pemphigus vulgaris, pemphigus fo liaceus, paraneoplastic pemphigus, or bullous pemphigoid. Three sera b locked F12 reactivity; two were from paraneoplastic pemphigus patients and the other was from the pemphigus vulgaris patient whose periphera l blood lymphocytes were used to make F12. All these sera recognized a 185-kD band that co-migrated with the polypeptide labeled by MoAb F12 on immunoblots. In addition, the IIF and IIEM staining patterns of Mo Ab F12 were similar to those observed with sera from two patients with paraneoplastic pemphigus. These observations suggest a relationship b etween MoAb F12 and the autoimmune response characterizing paraneoplas tic pemphigus patients' sera.