Figure 3. Effect of histamine receptor antagonists on histamine-induced inhibition of lactoferrin release.

Human PMNs (1×10⁶) were preincubated for 5 min, without or with the indicated concentrations of the H₄ receptor antagonists JNJ 7777120 (A), or JNJ 28307474 (B). Thereafter, histamine (1 μM) was added for 5 min. PMNs were then incubated on plates coated with fibrinogen in the presence of fMLP (0.1 μM). After 30 min, the concentration of lactoferrin in the extracellular milieu was measured by ELISA as described in Materials and Methods. The data are expressed as percent of controls (adherent cells stimulated with fMLP) and represent means ± sem of three to six separate experiments, each performed in triplicates.