Inverse relationship between multiple sclerosis and allergic respiratory diseases.

Th1 up-regulation seems to favour autoimmunity, while Th2 up-regulation seems to favour humoral immunity. Accordingly, subjects affected by atopic diseases (such as allergic respiratory diseases, ARDs) should be less prone to autoimmune diseases (such as multiple sclerosis, MS), and vice versa. The recent identification of Th17 cells, which seem to favour the development of both autoimmunity and allergy, led to the revision of the classic Th1/Th2 paradigm. We studied 200 MS patients and 200 controls to analyze the relationships between ARDs and MS. MS patients had less probability to suffer from ARDs (OR = 0.30, p < 0.001) and allergic rhinitis (OR = 0.25, p < 0.001), after adjusting for environmental factors. MS tended to be less severe when associated to ARDs. Our findings add some elements for the comprehension of immune mechanisms involved in MS pathogenesis and suggest to analyze other MS cohorts, in order to evaluate if MS patients affected by allergic diseases show particular clinical findings.