Antikeratin autoantibodies in the amyloid deposits of lichen amyloidosus and macular amyloidosis.

In order to characterize immunoglobulins found on amyloid deposits of lichen amyloidosus and macular amyloidosis, and elution from cryostat sections was performed with citrate buffer, glycine buffer, NaCl, and PBS. Resulting eluates (mainly IgG) were examined with dot immunoblotting and SDS-PAGE immunoblotting and were found to react with the human epidermal keratin of 50 and 67 kD. Antikeratin autoantibody activities in normal murine and human sera were examined using a dot immunoblotting assay. In murine sera, titers of IgG and IgM autoantibodies were higher in older mice. The human cord blood showed significantly lower IgM autoantibody titers, whereas IgG antibody titers showed no significant differences from adults' sera, probably due to the permeability of IgG through the placental barrier. A stronger antibody activity in older individuals was thought to be due to the repeated exposures to keratin proteins derived from apoptotic keratinocytes. Sera from lichen amyloidosus and macular amyloidosis patients did not show any difference from normal controls in their antikeratin titers. It was concluded that the patients with lichenoid or macular amyloidosis are capable of producing a normal level of antikeratin autoantibodies. However, the removal of opsonized keratin-type amyloid from the skin is slow or deficient due to as yet unknown factors.