AN ANTI-INTERLEUKIN-8 MONOCLONAL-ANTIBODY THAT INTERFERES WITH THE BINDING OF INTERLEUKIN-8 TO CELLULAR RECEPTORS AND THE ACTIVATION OF HUMAN BLOOD NEUTROPHILS

Interleukin 8 (IL-8) is a proinflammatory cytokine produced by a wide variety of cells, Interleukin 8 acts as a neutrophil activator and che motactic factor. In the current studies, we examined the properties of a monoclonal antibody against human IL-8. The estimated affinity of t he antibody was 1.74 x 10(7) liters/mol. The antibody interfered with the binding of radiolabeled recombinant human IL-8 (rhIL-8) to human b lood neutrophils (IC50 = 3 x 10(-7) M, at an IL-8 concentration of 2.4 nM), Neutrophil degranulation elicited by 5 x 10(-6)-4 x 10(-8) M rhI L-8 was blocked by the antibody at three-fold molar excess, However, a higher concentration of anti-IL-8 antibody was needed to suppress the chemotactic activity of rhIL-8, The inhibition of neutrophil chemotax is triggered by 2 x 10(-7)-2 x 10(-9) M rhIL-8 required 6 x 10(-5) M a ntibody, Similarly, a 300-fold molar excess of anti-IL-8 antibody [10( -5) M] was necessary to abrogate the increase in cytosolic free calciu m in neutrophils stimulated with 4 x 10(-8) M rhIL-8, In addition, epi tope analysis using synthetic peptides corresponding to different regi ons of the IL-8 molecule showed that peptide consisting of residues 44 -72 (corresponding to the C-terminal of the IL-8 molecule) competed wi th the antibody for binding to rhIL-8, Because IL-8 is an important in flammatory mediator in several human diseases, anti-IL-8 antibodies ma y have pharmacological potential.