Partial characterization of a cell-directed inhibitor of leukotaxis in human serum

A leukotactic defect is described in a man with a low cerebrospinal fluid leukocyte count in the presence of an acute listeria meningitis. On the basis of subsequent studies with his serum and normal human serum, a leukotactic inhibitor has been identified. This inhibitor, termed the cell-directed inhibitor (CDI), is relatively heat stable and nondialyzable. By ultracentrifugal analysis in sucrose density gradient, the inhibitor has been resolved into two activities with estimated sedimentation coefficients of 7 and 10 S. It interacts directly with neutrophils and monocytes to render them chemotactically defective. CDI also impairs the phagocytic function of neutrophils. Evidence is presented that an antagonist to the inhibitor is present in normal serum. CDI and its antagonist are probably normally occurring regulators of leukotaxis. In the patient studied, an elevated CDI serum level may be related to the development of the listeria infection and failure of cutaneous response to skin test antigens.