The vast majority of liver diseases involve, at least in part, an immunologic reaction either as a primary cause of liver injury or in response to an infectious agent. Primary biliary cirrhosis (PBC) and nonalcoholic steatohepatitis (NASH) are representative of the former while viral hepatitis B and C are typical of the latter. Historically, the diagnosis of a liver disease was based primarily on histology and in large part the types and locations of inflammatory cells within the liver parenchyma. This remains the case for alcoholic liver disease and the now epidemic fatty liver disease. However, increasingly specific liver disease diagnoses are made based upon specific immune responses signified by the presence of specific antibodies and other serologic findings. Currently, genetic tests in liver immunology are limited to HLA class II alleles in autoimmune hepatitis and hereditary hemochromatosis, the latter a result of variants in the HLA class I-like HFE gene resulting in dysregulation of the antimicrobial peptide hepcidin and subsequent iron overload. However, as our understanding of the genetic basis of liver diseases progresses, the use of individualized genetics will likely become increasing important in diagnosing many liver diseases and personalizing their treatments. In this chapter, we will review the common liver diseases with an immunologic basis with an emphasis on the diagnostic tools in current use (Table 4.1).
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