Immobilization of rolling NK cells on platelet-borne P-selectin under flow by proinflammatory stimuli, interleukin-12, and leukotriene B4.

Recruitment of leukocytes from bloodstream to extrahematic sites is tightly regulated by a variety of adhesion molecules that are expressed on the leukocytes and the vessel walls. In this manuscript, we describe the interactions between natural killer (NK) cells and activated, autologous platelets under physiologic flow. We found that surface-adherent human platelets are capable of recruiting human NK cells from flow and that this recruitment is characterized by an initial tethering followed by a rolling phase. Both phases were dependent on the adhesion molecule P-selectin and its counter-ligand on the NK cells (P-selectin glycoprotein ligand 1). Activation of rolling NK cells with inflammatory mediators commonly found in atherosclerotic plaques (interleukin-12 and leukotriene B4) causes immediate cessation of the rolling process and conversion to stationary adhesion. Blocking antibodies to the adhesion molecules membrane-activated complex-1 and leukocyte function antigen-1 inhibited this conversion. Our data suggest that platelets deposited at sites of vascular injury may provide an alternative substrate to endothelial cells for initial recruitment of NK cells to the vessel wall. This may result in extravasation of the NK cells if the appropriate chemotactic signal is applied. These data implicate the P-selectin and integrin family of adhesion molecules in the recruitment of NK cells to atherosclerotic sites.

F-18 FDG positron emission tomography in primary breast non-Hodgkin's lymphoma.

A 50-year-old woman had an irregular, mobile, firm right breast mass that became progressively larger in the past 3 months that measured 18 x 15 cm at the time of examination. She had no nipple discharge or skin changes. A 2-[18F]-fluoro-2-deoxy-D-glucose positron emission tomography (FDG PET) showed a ring-shaped breast uptake consisting of high peripheral glycolytic activity and a cold center most likely representing necrosis or hemorrhage despite the absence of a history of trauma, surgical intervention, chemotherapy, or radiation to the breast. Whole-body images did not show any evidence of lymph node involvement or distant metastases. These results were confirmed by computed tomography of the chest, abdomen, and pelvis. Cytologic examination of a fine-needle aspiration of the breast mass showed diffuse large B-cell, intermediate grade, non-Hodgkin's lymphoma. Although it occurs infrequently, primary breast lymphoma should be considered in patients with a breast mass that shows a ring-shaped FDG uptake. A PET scan, in contrast to other imagining techniques, offers the advantage of screening the entire body, excluding the presence of metastases, and confirming the primary origin of the breast lymphoma.