Immunofluorescence
Anne C. Lind
Joseph P. Gaut
Rosa M. Dávila
I. INTRODUCTION. Immunofluorescence studies are used to support fixed tissue diagnoses and to provide additional diagnostic and prognostic information as it relates to autoimmune diseases, vesiculobullous diseases, transplantation, and glomerular disease. Immunofluorescence requires fresh tissue submitted in a preservative nonfixative transport medium such as Michel’s medium, or fresh frozen tissue; currently, immunofluorescence is not routinely performed on formalin-fixed paraffinembedded (FFPE) tissue. For fresh tissue, the transport medium should be held at room temperature; temperature extremes should be avoided. A specialized microscope and a room where the majority of ambient light can be extinguished are required for either direct or indirect immunofluorescence examination.
II. DIRECT IMMUNOFLUORESCENCE
A. Skin/mucosa. Cutaneous/mucosal biopsies for immunofluorescence are stained with fluorescein-labeled antibodies to immunoglobulin (IgG, IgA, IgM), complement (C′3), and collagen IV. The patterns of staining that correlate with specific diseases are discussed in more detail with the corresponding diagnoses in the chapter on inflammatory disorders of the skin (Chap. 38). Patterns of staining include basement membrane (e-Fig. 56.1)* and intercellular (e-Fig. 56.2) positivity.
1. Bullous pemphigoid. A biopsy of perilesional tissue to include the edge of a blister is optimal. Some studies have reported a high false-negative rate for tissue from the lower extremity; if possible, tissue for direct immunofluorescence should be obtained from above the knee. Direct immunofluorescence is positive in approximately 85% to 90% of cases of bullous pemphigoid.
2. Pemphigus vulgaris. A biopsy of perilesional tissue, without including the edge of a blister, is optimal. Direct immunofluorescence is positive in approximately 90% to 95% of cases of pemphigus vulgaris.
3. Dermatitis herpetiformis. A biopsy of perilesional tissue, avoiding excoriated areas, is optimal. Direct immunofluorescence is positive in ˜80% of cases of dermatitis herpetiformis.
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