In vitro and in vivo effects of levamisole on monocyte chemotaxis in normal donors and patients with colorectal carcinoma.

Levamisole, a synthetic phenylimidazothiozole, was found to enhance chemotaxis of monocytes from both normal individuals and those with colorectal carcinoma. The optimum concentration in vitro varied among individuals but occurred most consistently at 200 micrograms/ml (approximately 10(-3) M). Overall relative increase in monocyte chemotaxis in 123 individuals was 29.3 +/- 4.2% (SE; p less than 0.0001 by paired t test comparison of individual baseline to stimulated values). The frequency of significant augmentation was the same in both patient and normal groups (30-45% of individuals tested). However, the degree of enhancement in vitro was greatest in patients with colorectal carcinoma. Twenty-nine volunteers ingested levamisole to evaluate in vivo effects on monocyte chemotaxis; significant increase occurred in 22. Both normal individuals and patients were stimulated to a similar degree and frequency. The immunomodulatory effects of levamisole may result from effects on monocyte function.