Immunopatholgenesis of hypersensitivity pneumonitis.

This review describes antigenic and host factors of possible significance in the immunopathogenesis of hypersensitivity pneumonitis (HP). Although certain immunologic studies suggest immune complex mechanisms in HP, recent experimental and clinical data accumulated support a role for cell-mediated immunity. In addition, some data support roles for anaphylactic and cytotoxic antibody-mediated reactivity as well. One type of reactivity alone may not be sufficient for production of HP, and local pulmonary immune responses may be most relevant to the pathogensis. Whether immune damage will be produced in an exposed individual or not may depend on the characteristics of the antigenic exposure as well as inherited and acquired individual differences in immunologic reactivity and possibly target organ sensitivity.