Differences in the anti-basement membrane zone antibodies in ocular and pseudo-ocular cicatricial pemphigoid

Ocular cicatricial pemphigoid (OCP) is a chronic autoimmune cicatrizing disease which affects the conjunctiva and other squamous epithelium, resulting in a scarring process. A similar process, limited only to the conjunctiva, observed in some patients using eye drops for the treatment of glaucoma, is called pseudo-ocular cicatricial pemphigoid (P-OCP). Immunofluorescence studies demonstrate deposition of immunoglobulins and complement components in the basement membrane zone (BMZ) of the conjunctiva and an anti-basement membrane zone antibody in the serum of patients. A striking association between OCP and MHC class II gene DQB1*0301 has been observed. The purpose of this study was to determine some of the differences in the binding of OCP and P-OCP sera to different lysate in an immunoblot assay, in an attempt to partially characterize the OCP and P-OCP antigens. Furthermore, we wanted to determine if the MHC class II gene association of P-OCP is similar to that of OCP.

We studied sera from 11 patients with active ocular cicatricial pemphigoid and seven patients with pseudo-ocular cicatricial pemphigoid and controls. Indirect immunofluorescence (IIF) studies were done using monkey esophagus and salt split normal human skin as substrate. A sensitive immunoblot assay (IBA) was developed using normal human epidermis, dermis and conjunctiva as substrate. Typing for MHC class II genes was performed on eight pseudo-ocular cicatricial pemphigoid patients by dot-blot analysis and compared to 38 matched controls.

Weak staining of the basement membrane zone was observed in nine of ten ocular cicatricial pemphigoid sera and five of seven pseudo-ocular cicatricial pemphigoid sera in the IIF assay using monkey esophagus. Using salt split human skin as substrate, ten of eleven ocular cicatricial pemphigoid sera demonstrated low titer weak binding to the epidermal side of the split. No consistent pattern of staining was seen with pseudo-ocular cicatricial pemphigoid sera. Ten of the 11 ocular cicatricial pemphigoid sera demonstrated binding to 230, 205, 160 and 85 kDa proteins in the IBA using normal human epidermis and conjunctiva lysates. When the lysates were first reacted with BP sera and then immunoblotted with ocular cicatricial pemphigoid sera, the 230, 160, and 86 kDa bands disappeared, and only the 205 kDa band persisted. The sera of five of seven pseudo-ocular cicatricial pemphigoid patients bound to 290, 230, 205, 180, 97, and 85 kDa proteins in the epidermis and conjunctiva. However, the 230, 205, 180, and 85 kDa proteins are depleted when the lysates are first reacted with BP and ocular cicatricial pemphigoid sera. In the dermal lysate, the pseudo-ocular cicatricial pemphigoid sera recognize 400, 290, 150 and 45 kDa proteins. None of these are absorbed by BP, ocular cicatricial pemphigoid or pemphigus vulgaris or epidermolysis bullosa acquisita sera. The 290 kDa proteins identified in the dermis and epidermis are distinct from each other. No binding was seen with control sera with the 3 lysates. Statistically, dot-blot analysis did not demonstrate a significant increase in the frequency of the MHC DQB1*0301 gene.

Patients with ocular cicatricial pemphigoid and pseudo-ocular cicatricial pemphigoid produce several autoantibodies. However, there are similarities and differences between them. The MHC class II genes associated with pseudo-ocular cicatricial pemphigoid are different from those with ocular cicatricial pemphigoid. This provides a new model system to study the immune abnormalities in idiopathic and drug-related organ specific autoimmunity.