The American journal of medicine
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Patients with multiple myeloma have been shown to have defective opsonization and C3 deposition. Previous studies have suggested that defective C3 deposition may be related to a failure of C3 activation in myeloma serum, the mechanism of which is unknown. We therefore decided to investigate the underlying mechanism responsible for the failure in C3 activation and deposition. ⋯ The defect in C3 activation and deposition in multiple myeloma cannot be explained on the basis of a single complement component abnormality but rather is due to a heterogeneous group of complement abnormalities. Although no correlation between in vitro abnormalities and clinical status was identified in this small group of patients, it is likely that the described complement defects play an important role in defective host defense in multiple myeloma.