[Anaphylactoid purpura and the complement system: particularly in terms of C3a and IgA (author's transl)]

We measured the immunoglobulin, beta1 C globulin, beta1E globulin, C3a, and CH50 in 20 patients with anaphylactoid purpura (Schönlein-Henoch purpura). IgA values proved to be elevated in 5 out of 11 cases. beta1 C globulin values were lower in 2 out of 8 cases and fell within the range of normalcy in the remaining 6 cases. beta1 E globulin values were normal in all cases measured (5 patients). A 130% increase in C3a was found in 7 out of 9 cases; patients with higher C3a values suffered from lasting petechial hemorrhages. It can, therefore, be concluded that the activation of the "alternative pathway" induced by IgA led to the release of C3a.