The objective is to define the signaling pathways activated by lipopolysaccharide (LPS) and other selected innate immunity stimuli, and the downstream inflammatory functional consequences, in human leukocytes in vitro. Adult (greater than or equal to 18 - 65 years old), nonpregnant, healthy volunteers will have 320 ml of whole blood collected by venipuncture in a monitored setting no more frequently than once every 8 weeks. No further interventions will be exercised upon the subjects. The whole blood will be fractionated into neutrophil, red blood cell, mononuclear cell, and plasma fractions using plasma-Percoll discontinuous centrifugation. Leukocytes will be subjected in vitro to inflammatory stimuli (eg, LPS), and selected signaling outcomes (eg, mitogen-activated protein kinase activation, Rho GTPase activation, protein-protein interactions) and functional measures (eg, chemotaxis, superoxide anion and cytokine production) quantified in the absence and presence of relevant chemical inhibitors (eg, SB203580, a p38 MAPK inhibitor). In each such experiment, cells from the daily donor will be used as paired controls to the in vitro experimental intervention (eg, SB203580 inhibitor vs. DMSO vehicle). Three or more repetitions (on different donors) of each specific experimental outcome, as necessary, will be performed to establish statistical significance of findings.