Autoimmune liver diseases.

Certain serum autoantibodies serve as useful diagnostic markers in AiLD; however, the etiology and pathogenesis of AiLD remain unknown. Although AiLD is characterized by the presence of autoantibodies and other humoral immune abnormalities, there is significant evidence that cell-mediated immune mechanisms are critical contributors to tissue injury in AiLD. The most sensitive and specific diagnostic immunologic marker for PBC is AMA. The availability of commercial kits that measure AMA directed against PDH-E2 (anti-M2) using ELISA may increase standardization of this test. AiH is characterized by the presence of ANA, SMA, and LKM. ANA are most commonly identified by IIFM using Hep-2 cells as substrate. IIFM is most commonly used to detect SMA and LKM, which, like AMA, can be identified using rodent (rat or mouse) combined kidney/stomach/liver tissue blocks as substrate. Most clinical laboratories with a capability to perform IIFMs therefore can identify the characteristic autoantibody patterns described in AiLD. As specific ELISAs become available, their widespread use in clinical laboratories also will facilitate the work-up of individuals with suspected AiLD.