No abstract

SummaryEarlier work has identified a cell population that replicates HIV-1 in the absence ofstandard T cell stimuli . The system consists of dendritic cells and memory T lymphocytes that emigrate from organ cultures of human skin and together support a productive infection with HIV-1 . These emigrants resemble cells that can be found in mucous membranes and that normally traffic in afferent lymph . Here, we report that a low level of infection in the dendritic cell can initiate extensive HIV-1 replication in cocultures with T cells . First we extended our earlier work to larger skin specimens from cadavers . As long as the organ cultures were set up within 36 h of death, the emigrant leukocytes were comparable to cells from fresh surgical specimens in number, phenotype, and function . These mixtures of dendritic cells and T cells provided the milieu for a productive infection with several virus isolates . When purified dendritic cells were separately pulsed with virus and then mixed with T cells that had not been pulsed with HIV-1, active infection ensued. The infectivity of HIV-pulsed dendritic cells persisted for at least 1 .5 d in culture, but was blocked if AZT was added during that time to block reverse transcription in the dendritic cells . The number of copies of proviral DNA in the dendritic cells corresponded to < 100 copies per 5 X 104 cells, but upon mixing with T cells, > 104 copies were found 5-7 d later. By contacting syngeneic T cells, extralymphoid depots of dendritic cells-even with a low viral burden as has been reported in vivo-may contribute to chronic HIV-1 replication in infected individuals .

P-glycoprotein (MDR-1) is a well-known transporter that mediates eff lux of chemotherapeutic agents from the intracellular milieu and thereby contributes to drug resistance. MDR-1 also is expressed by nonmalignant cells, including leukocytes, but physiologic functions for MDR-1 are poorly defined. Using an initial screening assay that included >100 mAbs, we observed that neutralizing mAbs MRK16, UIC2, and 4E3 against MDR-1 specifically and potently blocked basal-to-apical transendothelial migration of mononuclear phagocytes, a process that may mimic their migration into lymphatic vessels. Antagonists of MDR-1 then were used in a model of authentic lymphatic clearance. In this model, antigen-presenting dendritic cells (DC) migrate out of explants of cultured human skin and into the culture medium via dermal lymphatic vessels. DC and T cells derived from skin expressed MDR-1 on their surfaces. Addition of anti-MDR-1 mAbs MRK16, UIC2, or the MDR-1 antagonist verapamil to skin explants at the onset of culture inhibited the appearance of DC, and accompanying T cells, in the culture medium by approximately 70%. Isotype-matched control mAbs against other DC molecules including CD18, CD31, and major histocompatibility complex I did not block. In the presence of MDR-1 antagonists, epidermal DC were retained in the epidermis, in contrast to control conditions. In summary, this work identifies a physiologic function for MDR-1 during the mobilization of DC and begins to elucidate how these critical antigen-presenting cells migrate from the periphery to lymph nodes to initiate T lymphocyte-mediated immunity.

Seroma formation is a difficult problem to treat and prevent. Its sequelae include wound infection, dehiscence, and skin-flap necrosis. The purpose of this study was to determine the effects of fibrin sealant on seroma formation and wound healing. Seromas were created in a rat model by harvesting the latissimus dorsi muscle. In group I (n = 20), only the latissimus dorsi muscle was harvested. In group II (n = 20), the latissimus dorsi muscle was harvested and fibrin sealant applied. Seromas were routinely aspirated. In group III (n = 20), the latissimus dorsi muscle was harvested, and once a seroma was evident clinically, it was aspirated and injected with fibrin sealant. Fibrin sealant was created by combining virally deactivated fibrinogen and thrombin (American Red Cross, Rockville, Md.). In group I, 90 percent of the animals formed seromas compared with only 20 percent in group II. The average total fluid aspirated in group I was 21 cc versus 6 cc in group II. Sixty percent of the animals in group I and 5 percent in group II required serial drainage for chronic seromas. Skin-flap necrosis occurred in 80 percent of the animals in group I, in 10 percent of group II, and in 40 percent of group III. Histologic evaluation confirmed that group II underwent better wound healing. At necropsy, group I animals with seromas had gross capsular formation; this was not readily apparent in the fibrin sealant groups. We conclude that (1) the harvesting of the rat latissimus dorsi muscle is a reliable model for creating seromas, (2) fibrin sealant effectively prevents seroma formation when applied intraoperatively, (3) wound healing in the seroma rat model is improved with intraoperative fibrin sealant application, (4) closed injection of fibrin sealant for existing seromas cannot be recommended at this time, (5) virally deactivated fibrin sealant retains its hemostatic and adhesive properties, and (6) current clinical trials of virally deactivated fibrin sealant may facilitate its use in the United States.