Immunohistochemical analysis for C3d, C4d, IgG, IgG4, and CD123 in diagnosis of autoimmune skin diseases / 中南大学学报(医学版)

ABSTRACT

To assess the value of immunohistochemical analysis for expressions of C3d, C4d, IgG, IgG4, and CD123 in the diagnosis of autoimmune skin diseases.
 Methods: We investigated the expressions of C3d, C4d, IgG, IgG4, and CD123 in paraffin-embedded, formalin-fixed tissues from 27 lupus erythematosus cases, including 8 discoid lupus erythematosus (DLE) cases, 4 subacute cutaneous lupus erythematosus (SCLE) cases, and 15 systemic lupus erythematosus (SLE) cases. Tissues from 15 dermatomyositis (DM) cases, 15 bullous pemphigoid (BP) cases, and 15 pemphigus cases were examined by immunohistochemical analysis. The differences in expression rates of C3d, C4d, IgG, IgG4, and CD123 between immunohistochemical staining and direct immunofluorescence were compared in the diagnosis of these diseases.
 Results: In the lupus erythematosus group, the positive rates of C3d and C4d deposited along the dermoepidermal junction were 85.2% and 51.9%, respectively. In the dermatomyositis group, the positive rates of C3d and C4d deposited along the dermoepidermal junction were 40% and 0, respectively. The expressions of C3d and C4d in lupus erythematosus tissues were significantly higher than those in DM tissues (P<0.05). The expression of CD123 protein in skin lesions of the lupus group was significantly higher than that in the DM group (P<0.05). In the BP group, the positive rates of C3d and C4d deposited along the dermoepidermal junction were 100% and 86.7%, respectively. In the pemphigus group, the positive rates of C3d and C4d deposited in the intercellular space of keratinocytes were 100% and 60%, respectively. The expressions of IgG and IgG4 in pemphigus tissues were higher than those in BP tissues (P<0.05). And the ratios of IgG4 to IgG in the pemphigus group was significantly higher than that in the BP group (P<0.05).
 Conclusion: The assays of C3d and C4d define an important diagnostic adjunct in evaluation of lupus erythematosus, BP and pemphigus. In some cases, it may even replace the direct immunofluorescence as a diagnostic adjunct. The expression of CD123 possesses certain clinical significance for the differential diagnosis of lupus erythematosus, and IgG4 and IgG expressions have adjunctive diagnostic significance for pemphigus.