PAS x40 - RCPA

Examination of immunohistochemical stains:• these stains are used to look for abnormal proteins in glomeruli,tubular basement membranes and vessels, particularly immunecomplex deposits• there are differences between the patterns by directimmunofluorescence (IF) and immunoperoxidase (IP) methods– by IFo there may be up to moderate non-specific mesangial staining with antibodiesto IgM and C3o hyaline in glomeruli and arterioles stains with antibodies to IgM and C3o C4d may stain arteries non-specifically– by IP,o there may be up to moderate non-specific mesangial staining with antibodiesto IgM and C1qo hyaline in glomeruli and arterioles stains with antibodies to IgM and C1qo C4d stains arteries non-specifically but there is usually also non-specificmesangial staining– in both methods, there may be non-specific vascular staining with C3– enzymatic digestion of paraffin sections is required to expose antigensafter formalin fixation; this may cause background staining, especiallywith IgG