Immunofluorescence (IF) techniques

Direct IF (DIF)

Detects in vivoantibodies bound to tissue antigens in perilesional skin

Indirect IF (IIF)

Detects circulating serum antibodies (substrate sections react with serially diluted serum from patient → incubated with anti-IgG or other specific fluorescent dye-tagged antibody)

Best substrate: monkey esophagus (PV), guinea pig esophagus (PF), transitional rat bladder epithelium (PNP)

Salt-split-skin (SSS)
technique

Variant of IIF allowing distinction between different subepidermal blistering conditions with similar DIF findings; normal human skin incubated in 1 M NaCl for 48–72 h resulting in split at lamina lucida level; location of antibody binding to split (epidermal or dermal side) distinguishes different diseases