Defects of leukocyte locomotion in multiple myeloma.

23 patients with multiple myeloma of IgG, IgA and light chain type, one patient with benign monoclonal IgE gammopathy and 23 healthy controls were investigated for their leukocyte locomotion (LL), for the ability of their sera to generate chemotactic factors upon activation with zymosan, and for inhibitory effects of their sera upon LL. While no significant impairment of the patients' LL was observed when casein was used as cytotaxin, LL was markedly reduced in myeloma patients with zymosan activated control serum as chemoattractant. The ability of serum to generate chemotactic factors upon activation with zymosan was similar in patients and controls, but preincubation of control leukocytes with sera derived from patients with multiple myeloma caused a significant inhibition of LL (p less than 0.001). This LL-inhibitory serum effect was not correlated with the type of paraproteinemia. We conclude that the impairment of LL in multiple myeloma and the LL-inhibitory serum effect might contribute to the increased susceptibility to infections in that disorder.