Viruses: the culprits of autoimmune diseases?

There are obvious difficulties in attempting to ascribe a viral aetiology to autoimmune diseases. Nevertheless, there are certain points relating to this issue which are generally recognized as fundamental, even if these are hard to resolve. Any theory must account for autoantigenic specificity and the polygenic factors conferring susceptibility to disease. The classical dogmas about loss of T or B cell tolerance or a combination of these cell populations are still valid, but the factors that lead to the breakdown of tolerance are more complex than was formerly envisaged. The complexities of host defense against viral infections are increasingly apparent. Furthermore, the classical, sharp distinction between innate or non-specific immunity and specific immunity is no longer tenable because these contribute to host defense in an integrated manner. The chain of events that lead from initial infection to sustained autoimmunity is likely to depend on quantitative factors, which can never be spelt out adequately in descriptive terms.