Infection-induced NETosis is a dynamic process involving neutrophil multitasking in vivo.

Neutrophil extracellular traps (NETs) are released as neutrophils die in vitro in a process requiring hours, leaving a temporal gap that invasive microbes may exploit. Neutrophils capable of migration and phagocytosis while undergoing NETosis have not been documented. During Gram-positive skin infections, we directly visualized live polymorphonuclear cells (PMNs) in vivo rapidly releasing NETs, which prevented systemic bacterial dissemination.

Tonic inhibition of chemotaxis in human plasma.

We found exaggerated chemotaxis in plasma treated with EDTA and thought that the EDTA might itself be inhibiting a tonic inhibitor(s) of chemotaxis. Our plasma fractionations suggested that evidence should be sought for a lipid moiety carrying this activity, and on spectrometry (LC-MS-MS together with GC-MS analyses), the biologically active but not the inactive fraction contained oleic and arachidonic acids. Because fatty acids are largely protein bound, we flooded plasma preparations with delipidated albumin, reasoning that it would bind enough fatty acids, including inhibitory ones, to counter their tonic inhibition.

Clocking the Lyme spirochete.

In order to clear the body of infecting spirochetes, phagocytic cells must be able to get hold of them. In real-time phase-contrast videomicroscopy we were able to measure the speed of Borrelia burgdorferi (Bb), the Lyme spirochete, moving back and forth across a platelet to which it was tethered. Its mean crossing speed was 1,636 microm/min (N = 28), maximum, 2800 microm/min (N = 3).

Phagocytic function of human blood polymorphonuclear leukocytes in the presence of carrageenan, a potential vaginal microbicide.

Carrageenan is currently undergoing clinical trials as the active constituent of a vaginal gel product for use as a female-controlled option to prevent the transmission of HIV during sexual intercourse. Here we show that in the presence of 0.5 mg/ml of carrageenan, human blood polymorphonuclear leukocytes (PMN) do not ingest this material, as evidenced by a lack of progressive vacuolization, but can ingest microorganisms present in the medium, excluding adjacent carrageenan.

Tick saliva reduces adherence and area of human neutrophils.

During natural infection with the agent of Lyme disease, Borrelia burgdorferi, spirochetes are delivered with vector saliva, which contains anti-inflammatory and antihemostatic activities. We show here that the saliva of ixodid ticks reduces polymorphonuclear leukocyte (PMN) adhesion via downregulation of beta2-integrins and decreases the efficiency of PMN in the uptake and killing of spirochetes. Inhibition of integrin adhesion and signaling reduces anti-inflammatory functions of PMN.