Pathological cell aggregates in bone marrow cultures from patients with various hematological diseases.

Non-clonal growth of macroscopic cell aggregates in methylcellulose cultures of abnormal marrow is described. They were seen in all patients with Graft-versus-Host Disease, graft rejection, and autoimmune disease presumably directed against hemopoietic cells, we found them in 35% of patients with primary hematological neoplasias and rarely in patients with solid tumors. They were never encountered in 80 healthy controls. The aggregates originated from small cell clumps which sedimented with the "buffy coat" in contrast to normal bone marrow particles. They contained tumor cells, grafted myeloid cells, or target cells of autoimmune disease in association with a widely varying amount of macrophages. Preliminary results suggest that the frequency of macrophages within the aggregates correlates inversely with the aggressiveness of the clinical condition. We propose that appearance of such aggregates in an indicator of immune activation; we expect that further quantitation of the phenomenon will reveal important clinical correlations and provide a model for the study of host defense to "foreign" cells.