Vasculitis: immunological aspects.

The laboratory approach to patients with a vasculitic syndrome is of limited help in defining the diagnosis but may provide clues as to the pathogenesis (immune complex-mediated or cell-mediated reaction). Serial determinations of immune complexes or complement levels can also serve as the basis for assessment of disease activity and therapeutic interventions in some patients. In addition to angiographic findings there is only one way of establishing a tentative diagnosis of vasculitis: by histological demonstration.