Diagnosis: Immunology: Antibodies
• An adaptive immune response is specific to the antigen (immunogen) that stimulated it. However, many naturally occurring immunogens display multiple epitopes that stimulate a variety of immune responses.
• Cross-reactivity is the reaction between an antibody and an antigen in which the antigen differs from the immunogen.
• In a broader sense, cross-reactivity applies to other immune responses as well. For example, despite the high specificity of T-cell responses, some T-cell clones may react against more than a single antigen.
• Cross-reactivity of immune cells has been documented in humans. For example, influenza virus–specific CD8+ T cells were shown to react against hepatitis virus antigen.
• Cross-reactivity contributes to the vigorous response of T cells to allogeneic major histocompatibility complexes (MHC). T cells, which have been exposed to antigens, may cross-react with allogeneic cells.
