How infection can trigger autoimmunity

Infectious mononucleosis fifty years after the discovery of the Paul-Bunnell test

The Paul-Bunnell test, now 50 years old, is still of fundamental importance in the diagnosis of infectious mononucleosis, even though various immunologic methods have been developed in clinical practice to identify constituents of the Epstein-Barr virus (EBV). The demonstration of sheep red cell agglutinins in infectious mononucleosis (Paul-Bunnell) was in fact the first observation of the presence of heterophil antibodies in this viral disease which was later shown to evoke a polyclonal antibody response to a wide spectrum of autoantigens as well. The selective tropism of EBV for B lymphocytes and the reactivity of T lymphocytes to these infected B lymphocytes are the pathophysiological elements characteristic of infectious mononucleosis, and are the reason for this massive antibody response.

Atopy as a minimal immunodeficiency?

Despite impressive recent advances in the understanding of the chemical and cellular bases of the reaginic response, the pathogenesis of atopic diseases still remains a matter of speculation. The frequent finding of atopic diseases in some primary immunodeficiencies such as selective IgA deficiency and the Wiskott-Aldrich syndrome offers a unique opportunity for studying the immune mechanisms underlying the genesis of atopy. Recent studies in subjects with selective IgA deficiency have challenged the well known hypothesis that atopy is the result of defective "immune exclusion" by the secretory immune system. A number of immunological features found in the primary immunodeficiencies associated with atopic disorders suggest that defective homeostatic mechanisms regulating reaginic responses may play a major role in the pathogenesis of atopy. A thorough analysis of these disease combinations may help to generate new working hypotheses concerning the immune pathogenesis of atopic diseases.