[Immunoglobulins and the complement system in Horton's headache].

In 39 patients with Horton's headache (bgh) and 70 controls the total complement level and the levels of its C3 and C4 fractions, as well as IgG, IgA and IgM levels were determined. It was found that in bgh patients the mean level of the C3 fraction was significantly below that in the control group, while the C4 level was still within normal range. The levels of immunoglobulins were not statistically significantly different in these groups with the exception of IgA which was significantly lower in bgh cases. The author thinks that low C3 fraction level may be a part of the clinical pattern of bgh and is due to activation of the complement system on the alternative pathway. On the other hand, bgh attacks could not be qualified into any known type of allergic reaction.