Lymphokine-induced macrophage aggregation: involvement of cyclic-GMP and microtubules.

Human lymphokine (LK) is known to induce guinea pig macrophage aggregation. This effect can be quantitatively measured with a Born modified platelet aggregometer. This method has been well correlated with the state of delayed hypersensitivity. Previous findings about the mechanism of action of the aggregation indicated that this aggregation is not due to an increase in the cellular level of c-AMP. It is doubtful whether c-AMP is a messenger of the LK action. Using a radio-immunoassay, small but significant increases were found in c-GMP levels of LK-aggregated macrophages. In addition, exogenous dibutyryl c-GMP and carbamylcholine induced a macrophage aggregation, as did the divalent cation ionophore A-23187. These data, together with the fact that LK-induced macrophage aggregation is inhibited by colchicine and at 0 degree C, suggest that microtubule polymerization is involved in this process.