Conjugates of dendritic cells and memory T lymphocytes from skin facilitate productive infection with HIV-1

Experimentally, a productive infection with HIV-1 requires that virus be administered to T cells that are activated by mitogens. We describe a productive milieu for HIV-1 within the confines of normal skin that does not require standard stimuli. The milieu consists of dendritic cells and T cells that emigrate from skin and produce distinctive stable, nonproliferating conjugates. These conjugates, upon exposure to each of seven different HIV-1 isolates, begin to release high levels of virus progeny within 4 days. Numerous infected syncytia, comprised of both dendritic and T cells, rapidly develop. We propose that conjugates of dendritic cells and T cells, as found in the external linings of organs involved in sexual transmission of HIV-1, represent an important site for the productive phase of HIV-1 infection. Because the affected T cells carry the memory phenotype, this site additionally provides a mechanism for the chronic depletion of CD4+ memory cells in HIV-1 disease.

Dendritic cells freshly isolated from human blood express CD4 and mature into typical immunostimulatory dendritic cells after culture in monocyte-conditioned medium

A procedure has been developed to isolate dendritic cells to a high degree of purity from fresh blood. Prior enrichment methods have relied upon an initial 1-2-d culture period. Purified fresh isolates lack the characteristic morphology, phenotype, and immunostimulatory function of dendritic cells. The purified cells have the appearance of medium sized lymphocytes and express substantial levels of CD4, but lack the T cell molecules CD3, CD8, and T cell receptor. When placed in culture, the cells mature in a manner resembling the previously described, cytokine-dependent maturation of epidermal dendritic cells (Langerhans cells). The cells enlarge and exhibit many cell processes, express much higher levels of major histocompatibility complex class II and a panel of accessory molecules for T cell activation, and become potent stimulators of the mixed leukocyte reaction. Among the many changes during this maturation process are a fall in CD4 and the appearance of high levels of B7/BB1, the costimulator for enhanced interleukin 2 production in T cells. These changes are not associated with cell proliferation, but are dependent upon the addition of monocyte-conditioned medium. We suggest that the freshly isolated CD4-positive blood dendritic cells are recent migrants from the bone marrow, and that subsequent maturation of the lineage occurs in tissues in situ upon appropriate exposure to cytokines.

Prevention of relapse in residual depression by cognitive therapy: a controlled trial

BACKGROUND

Previous studies indicate that depressed patients with partial remission and residual symptoms following antidepressant treatment are common and have high rates of relapse. There is evidence that cognitive therapy may reduce relapse rates in depression.

METHODS

One hundred fifty-eight patients with recent major depression, partially remitted with antidepressant treatment (mean daily doses equivalent to 185 mg of amitriptyline or 33 mg of fluoxetine) but with residual symptoms of 2 to 18 months' duration, were included in a controlled trial. Subjects were randomized to receive clinical management alone or clinical management plus cognitive therapy for 16 sessions during 20 weeks, with 2 subsequent booster sessions. Subjects were assessed regularly throughout the 20 weeks' treatment and for a further year. They received continuation and maintenance antidepressants at the same dose throughout.

RESULTS

Cognitive therapy reduced relapse rates for acute major depression and persistent severe residual symptoms, in both intention to treat and treated per protocol samples. The cumulative relapse rate at 68 weeks was reduced significantly, from 47% in the clinical management control group to 29% with cognitive therapy (hazard ratio 0.54; 95% confidence interval, 0.32-0.93; intention to treat analysis). Cognitive therapy also increased full remission rates at 20 weeks but did not significantly improve symptom ratings.

CONCLUSION

In this difficult-to-treat group of patients with residual depression who showed only partial response despite antidepressant treatment, cognitive therapy produced worthwhile benefit.

Replication of HIV-1 in dendritic cell-derived syncytia at the mucosal surface of the adenoid

Human immunodeficiency virus-type 1 (HIV-1) replicates actively in infected individuals, yet cells with intracellular depots of viral protein are observed only infrequently. Many cells expressing the HIV-1 Gag protein were detected at the surface of the nasopharyngeal tonsil or adenoid. This infected mucosal surface contained T cells and dendritic cells, two cell types that together support HIV-1 replication in culture. The infected cells were multinucleated syncytia and expressed the S100 and p55 dendritic cell markers. Eleven of the 13 specimens analyzed were from donors who did not have symptoms of acquired immunodeficiency syndrome (AIDS). The interaction of dendritic cells and T cells in mucosa may support HIV-1 replication, even in subclinical stages of infection.

Efficient interaction of HIV-1 with purified dendritic cells via multiple chemokine coreceptors

HIV-1 actively replicates in dendritic cell (DC)-T cell cocultures, but it has been difficult to demonstrate substantial infection of purified mature DCs. We now find that HIV-1 begins reverse transcription much more efficiently in DCs than T cells, even though T cells have higher levels of CD4 and gp120 binding. DCs isolated from skin or from blood precursors behave similarly. Several M-tropic strains and the T-tropic strain IIIB enter DCs efficiently, as assessed by the progressive formation of the early products of reverse transcription after a 90-min virus pulse at 37 degrees C. However, few late gag-containing sequences are detected, so that active viral replication does not occur. The formation of these early transcripts seems to follow entry of HIV-1, rather than binding of virions that contain viral DNA. Early transcripts are scarce if DCs are exposed to virus on ice for 4 h, or for 90 min at 37 degrees C, conditions which allow virus binding. Also the early transcripts once formed are insensitive to trypsin. The entry of a M-tropic isolates is blocked by the chemokine RANTES, and the entry of IIIB by SDF-1. RANTES interacts with CCR5 and SDF-1 with CXCR4 receptors. Entry of M-tropic but not T-tropic virus is ablated in DCs from individuals who lack a functional CCR5 receptor. DCs express more CCR5 and CXCR4 mRNA than T cells. Therefore, while HIV-1 does not replicate efficiently in mature DCs, viral entry can be active and can be blocked by chemokines that act on known receptors for M- and T-tropic virus.

A physiologic function for p-glycoprotein (MDR-1) during the migration of dendritic cells from skin via afferent lymphatic vessels

P-glycoprotein (MDR-1) is a well-known transporter that mediates efflux 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.

Rapid infection of oral mucosal-associated lymphoid tissue with simian immunodeficiency virus

The early events during infection with an immunodeficiency virus were followed by application of pathogenic simian immunodeficiency virus atraumatically to the tonsils of macaques. Analyses by virologic assays and in situ hybridization revealed that the infection started locally in the tonsils, a mucosal-associated lymphoid organ, and quickly spread to other lymphoid tissues. At day 3, there were few infected cells, but then the number increased rapidly, reaching a high plateau between days 4 and 7. The infection was not detected in the dendritic cell-rich squamous epithelium to which the virus was applied; instead, it was primarily in CD4+ tonsillar T cells, close to the specialized antigen-transporting epithelium of the tonsillar crypts. Transport of the virus and immune-activating stimuli across this epithelium would allow mucosal lymphoid tissue to function in the atraumatic transmission of immunodeficiency viruses.

Low levels of HIV-1 infection in cutaneous dendritic cells promote extensive viral replication upon binding to memory CD4+ T cells

Earlier work has identified a cell population that replicates HIV-1 in the absence of standard 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 10(4) cells, but upon mixing with T cells, > 10(4) 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.

How does cognitive therapy prevent relapse in residual depression? Evidence from a controlled trial

This study examined the cognitive mediation of relapse prevention by cognitive therapy (CT) in a trial of 158 patients with residual depression. Scores based on agreement with item content of 5 questionnaires of depression-related cognition provided no evidence for cognitive mediation. A measure of the form of response to those questionnaires, the number of times patients used extreme response categories ("totally agree" and "totally disagree"), showed significant and substantial prediction of relapse, differential response to CT. and conformity to mediational criteria. CT reduced relapse through reductions in absolutist, dichotomous thinking style. CT may prevent relapse by training patients to change the way that they process depression-related material rather than by changing belief in depressive thought content.

Adipose atrophy in cancer cachexia: morphologic and molecular analysis of adipose tissue in tumour-bearing mice

Extensive loss of adipose tissue is a hallmark of cancer cachexia but the cellular and molecular basis remains unclear. This study has examined morphologic and molecular characteristics of white adipose tissue in mice bearing a cachexia-inducing tumour, MAC16. Adipose tissue from tumour-bearing mice contained shrunken adipocytes that were heterogeneous in size. Increased fibrosis was evident by strong collagen-fibril staining in the tissue matrix. Ultrastructure of 'slimmed' adipocytes revealed severe delipidation and modifications in cell membrane conformation. There were major reductions in mRNA levels of adipogenic transcription factors including CCAAT/enhancer binding protein alpha (C/EBPalpha), CCAAT/enhancer binding protein beta, peroxisome proliferator-activated receptor gamma, and sterol regulatory element binding protein-1c (SREBP-1c) in adipose tissue, which was accompanied by reduced protein content of C/EBPalpha and SREBP-1. mRNA levels of SREBP-1c targets, fatty acid synthase, acetyl CoA carboxylase, stearoyl CoA desaturase 1 and glycerol-3-phosphate acyl transferase, also fell as did glucose transporter-4 and leptin. In contrast, mRNA levels of peroxisome proliferators-activated receptor gamma coactivator-1alpha and uncoupling protein-2 were increased in white fat of tumour-bearing mice. These results suggest that the tumour-induced impairment in the formation and lipid storing capacity of adipose tissue occurs in mice with cancer cachexia.

CD69, HLA-DR and the IL-2R identify persistently activated T cells in psoriasis vulgaris lesional skin: blood and skin comparisons by flow cytometry

Many lymphocyte-activation-associated molecules are observed by immunohistochemistry in psoriasis vulgaris lesional skin. Non-T cells in lesional skin also express these molecules. We quantitatively measured the number of T cells expressing cell surface activation-associated molecules (CD69, CD25, CD122, HLA-DR) and co-stimulatory molecules (CD28, CTLA-4, CD80, CD86), including a Type 2 T cell marker (CD30) and CD11b, by flow cytometry of skin and peripheral blood. T cells in single cell suspensions of psoriatic lesional-epidermis-expressed HLA-DR (86%), CD69 (59%), CD25 (55%), CD122 (44%), and CD28 (91%). Dermal T cells showed similar percentages except for CD69 (17%). CD69 was found directly in lesional skin biopsies by immunohistochemistry. Both CD4 and CD8 subsets from lesional skin contained large populations of CD25+ cells with a bias towards CD8 activation in the epidermis and towards CD4 activation in the dermis. CD86, CD80, CTLA-4, CD30 and CD11b were expressed by less than 23% of the T cell populations from both the epidermis and dermis. CD30+CD4+ cells were found two-fold over CD8+ T cells. These results show that the majority of lesional lymphocytes are persistently activated. We also found the majority of Type 2 associated markers primarily on the CD4+ epidermal T cell population. Psoriatic blood contained elevated levels of T cells expressing CD25, primarily within the CD8+ subset. Thus the majority of lesional T cells expressed the three primary activation markers, while psoriatic blood T cells were distinguished by an increase in CD25, specifically within the CTL population.

Infectious and whole inactivated simian immunodeficiency viruses interact similarly with primate dendritic cells (DCs): differential intracellular fate of virions in mature and immature DCs

As potential targets for human immunodeficiency virus type 1 and simian immunodeficiency virus (HIV-1 and SIV), dendritic cells (DCs) likely play a significant role in the onset and spread of infection as well as in the induction of antiviral immunity. Using the SIV-macaque system to study the very early events in DC-virus interactions, we compared chemically inactivated SIV having conformationally and functionally intact envelope glycoproteins (2,2'-dithiodipyridine [AT-2] SIV) to infectious and heat-treated SIV. Both human and macaque DCs interact similarly with SIV without detectable effects on DC viability, phenotype, or endocytic function. As assessed by measuring cell-associated viral RNA, considerable amounts of virus are captured by the DCs and this is reduced when the virus is heat treated or derived from a strain that expresses low levels of envelope glycoprotein. Immunostaining for SIV proteins and electron microscopy indicated that few intact virus particles are retained at the periphery of the endocytically active, immature DCs. This contrasts with a perinuclear localization of numerous virions in large vesicular compartments deeper within mature DCs (in which macropinocytosis is down-regulated). Both immature and mature DCs are capable of clathrin-coated pit-mediated uptake of SIV, supporting the notion that the receptor-mediated uptake of virus can occur readily in mature DCs. While large numbers of whole viruses were preferentially found in mature DCs, both immature and mature DCs contained similar amounts of viral RNA, suggesting that different uptake/virus entry mechanisms are active in immature and mature DCs. These findings have significant implications for cell-to-cell transmission of HIV-1 and SIV and support the use of AT-2 SIV, an authentic but noninfectious form of virus, as a useful tool for studies of processing and presentation of AT-2 SIV antigens by DCs.

Vimentin-positive, c-kit-negative interstitial cells in human and rat uterus: a role in pacemaking?

The mechanism underlying spontaneous pacemaker potential in the uterus is not clearly understood. Several spontaneously active smooth muscles have interstitial cells of Cajal (ICCs) or ICC-like cells. We therefore examined cells from freshly dispersed uterine muscle strips (from pregnant human and rat myometrium) and in situ uterine preparations to determine the cell types present. Both preparations revealed numerous ICC-like cells; they were multipolar, with spider-like projections and enlarged central regions. These cells were readily distinguished from uterine myocytes by their morphology and ultrastructure, i.e., no myofilaments, numerous mitochondria, caveolae, and filaments. In addition, the ICC-like cells were noncontractile. These cells were negative to c-kit, a classic marker for ICCs. They stained positive for the intermediate filament, vimentin, a marker for cells of mesenchymal origin but not differentiated myocytes. The ICC-like cells had a more or less stable resting membrane potential of -58+/-7 mV compared with smooth-muscle cells, -65+/-13 mV, and produced outward current in response to voltage clamp pulses. However, in contrast with uterine myocytes, inward currents were not observed. This is the first description of ICC-like cells in myometrium and their role in the uterus is discussed, as possible inhibitors of intrinsic smooth-muscle activity.

A practical approach to vascular access for hemodialysis and predictors of success

PURPOSE

The long-term results and predictors of success for vascular access at The Toronto Hospital were studied. This report describes the access program and emphasizes the role of the vascular access coordinator.

METHODS

A total of 384 consecutive patients underwent 466 vascular access procedures. The access program is centered around a dedicated, full-time vascular access coordinator, who is a registered nurse and is responsible for all aspects of access care, including follow-up. Outcome variables were collected prospectively. Primary, primary-assisted, and secondary success was determined by means of Kaplan-Meier analysis, and the stepwise Cox proportional hazards model was used for multivariate analysis of the factors that were independently predictive of primary success.

RESULTS

There were 235 autogenous arteriovenous fistulae (AVFs) and 231 arteriovenous grafts (AVGs). The cumulative primary, assisted-primary, and secondary success (patent and functional for effective dialysis) at 24 months for all 466 cases combined was 36% +/- 3%, 54% +/- 3%, and 66% +/- 3%, respectively. The primary success for AVFs and AVGs at 2 years was 54% +/- 4% and 18% +/- 4%, respectively (P <.001; log-rank test); the primary-assisted success for AVFs and AVGs at 2 years was 62% +/- 4% and 44% +/- 6%, respectively (P <.001; log-rank test); and the secondary success for AVFs and AVGs at 2 years was 70% +/- 4% and 60% +/- 5%, respectively (P =.331; log-rank test). Stratification of variables revealed significant benefit for AVFs (P =.001), the female sex (P =.014), and the absence of diabetes mellitus (P =.001). Multivariate analysis with Cox regression determined that access type (AVF vs AVG; P =.001) and diabetes mellitus (P =.024) were independently predictive of primary success. The improved clinical coordination of access patients with the initiation of the vascular access program resulted in a significant reduction in length of hospital stay before and after the program was organized (2.5 +/- 0.06 vs 1.1 +/- 0.03 days; P =.001).

CONCLUSION

The organization of a vascular access program in a practical and cost-effective way for reduced length of hospital stay is streamlined through a dedicated access coordinator, who ensures an integrated, multidisciplinary approach. The results for the Cox model is useful when discussing the anticipated results of access procedures with individual patients.

Adipose tissue and fetal programming

Adipose tissue function changes with development. In the newborn, brown adipose tissue (BAT) is essential for ensuring effective adaptation to the extrauterine environment, and its growth during gestation is largely dependent on glucose supply from the mother to the fetus. The amount, location and type of adipose tissue deposited can also determine fetal glucose homeostasis. Adipose tissue first appears at around mid-gestation. Total adipose mass then increases through late gestation, when it comprises a mixture of white and brown adipocytes. BAT possesses a unique uncoupling protein, UCP1, which is responsible for the rapid generation of large amounts of heat at birth. Then, during postnatal life some, but not all, depots are replaced by white fat. This process can be utilised to investigate the physiological conversion of brown to white fat, and how it is re-programmed by nutritional changes in pre- and postnatal environments. A reduction in early BAT deposition may perpetuate through the life cycle, thereby suppressing energy expenditure and ultimately promoting obesity. Normal fat development profiles in the offspring are modified by changes in maternal diet at defined stages of pregnancy, ultimately leading to adverse long-term outcomes. For example, excess macrophage accumulation and the onset of insulin resistance occur in an adipose tissue depot-specific manner in offspring born to mothers fed a suboptimal diet from early to mid-gestation. In conclusion, the growth of the different fetal adipose tissue depots varies according to maternal diet and, if challenged in later life, this can contribute to insulin resistance and impaired glucose homeostasis.

Coexpression of NF-kappa B/Rel and Sp1 transcription factors in human immunodeficiency virus 1-induced, dendritic cell-T-cell syncytia

Productive infection of T cells with human immunodeficiency virus 1 (HIV-1) typically requires that the T cells be stimulated with antigens or mitogens. This requirement has been attributed to the activation of the transcription factor NF-kappa B, which synergizes with the constitutive transcription factor Sp1 to drive the HIV-1 promoter. Recently, we have found that vigorous replication of HIV-1 takes place in nonactivated memory T cells after syncytium formation with dendritic cells (DCs). These syncytia lack activated cells as determined by an absence of staining for Ki-67 cell cycle antigen. The expression and activity of NF-kappa B and Sp1 were, therefore, analyzed in isolated T cells and DCs from humans and mice. We have used immunolabeling, Western blot analysis, and electrophoretic mobility shift and supershift assays. T cells lack active NF-kappa B but express Sp1 as expected. DCs express high levels of all known NF-kappa B and Rel proteins, with activity residing primarily within RelB, p50, and p65. However, DCs lack Sp1, which may explain the failure of HIV-1 to replicate in purified DCs. Coexpression of NF-kappa B and Sp1 occurs in the heterologous DC-T-cell syncytia that are induced by HIV-1. Therefore, HIV-1-induced cell fusion brings together factors that upregulate virus transcription. Since DCs and memory T cells frequently traffic together in situ, these unusual heterologous syncytia could develop in infected individuals and lead to chronic HIV-1 replication without ostensible immune stimulation.

Anaphylaxis after thrombin injection of a femoral pseudoaneurysm: recommendations for prevention

After the injection treatment of a femoral pseudoaneurysm, an anaphylactic reaction occurred in a patient undergoing hemodialysis who previously had repeated exposure to thrombin. Before injecting bovine thrombin in patients with a history of prior exposure, we recommend that they undergo skin prick testing to detect possible allergy.

Canarypox virus-induced maturation of dendritic cells is mediated by apoptotic cell death and tumor necrosis factor alpha secretion

Recombinant avipox viruses are being widely evaluated as vaccines. To address how these viruses, which replicate poorly in mammalian cells, might be immunogenic, we studied how canarypox virus (ALVAC) interacts with primate antigen-presenting dendritic cells (DCs). When human and rhesus macaque monocyte-derived DCs were exposed to recombinant ALVAC, immature DCs were most susceptible to infection. However, many of the infected cells underwent apoptotic cell death, and dying infected cells were engulfed by uninfected DCs. Furthermore, a subset of DCs matured in the ALVAC-exposed DC cultures. DC maturation coincided with tumor necrosis factor alpha (TNF-alpha) secretion and was significantly blocked in the presence of anti-TNF-alpha antibodies. Interestingly, inhibition of apoptosis with a caspase 3 inhibitor also reduced some of the maturation induced by exposure to ALVAC. This indicates that both TNF-alpha and the presence of primarily apoptotic cells contributed to DC maturation. Therefore, infection of immature primate DCs with ALVAC results in apoptotic death of infected cells, which can be internalized by noninfected DCs driving DC maturation in the presence of the TNF-alpha secreted concomitantly by exposed cells. This suggests an important mechanism that may influence the immunogenicity of avipox virus vectors.

Maturation and migration of cutaneous dendritic cells

Dendritic cells have been isolated from the epidermis, dermis, and lymphatics of skin. Cells from each cutaneous compartment can exhibit the distinct morphology, surface phenotype, and strong T-cell-stimulating activity of dendritic cells that are isolated from other organs. Of importance are the mechanisms by which the maturation and movement of dendritic cells are regulated within intact tissues. Epidermal dendritic cells turn over slowly in the steady state. Stimuli, including contact allergens and transplantation, perhaps by inducing a release of cytokines such as granulocyte macrophage-colony-stimulating factor, mobilize these dendritic cells into the dermis and lymph. This migration is accompanied by the maturation of dendritic cell functions; e.g., antigen-presenting major histocompatibility complex molecules and B7 costimulators increase markedly. On the other hand, there is a sizable, steady-state flux of dendritic cells in afferent lymph draining the skin, which suggests a constant traffic through the dermis that is independent of sessile epidermal dendritic cells. When explants of skin are placed in organ culture, dendritic cells emigrate into the medium for 1-3 d. The dendritic cells are mature and can bind tightly to small memory T cells that also migrate in these cultures. The emigrated mixtures of dendritic cells and T cells should be useful in the study of many clinical states. This is illustrated by recent experiments showing that migratory skin cells are readily infected with human immunodeficiency virus (HIV)-1. A strong productive infection takes place in the absence of exogenous cytokines, foreign sera, or mitogens or antigens. The dendritic cell-T-cell conjugates are the essential site for infection. This cellular milieu may model events during the sexual transmission of HIV-1, where relevant mucosal surfaces are covered by skin-like epithelia. The capture of CD4+ memory T cells by dendritic cells may explain the chronic drain of immune memory in HIV infection.

Dendritic cells and the replication of HIV-1

Dendritic cells (DCs) are a distinct lineage of white cells that arise from CD34+ progenitors in the bone marrow. DCs exhibit many specializations that lead to efficient antigen capture and presentation to T cells, both CD4+ helpers and CD8+ killers. In several human tissues, DCs express the CD4 receptor for HIV-1. Some early reports described the explosive infection of blood-derived DCs by HIV-1 and a severe compromise of their presenting function. In contrast, other studies described active HIV-1 replication when DCs were interacting with CD4+ T cells. This productive infection could begin with a low viral burden in DCs but required that the DCs retain their normal binding and stimulatory function for T cells. In this review we first summarize those features of the DC system that seem pertinent to HIV-1 infection. Then we consider the current literature on the interaction of HIV-1 with DCs, from several different tissues, in HIV-1-infected patients or following challenge with HIV-1 in vitro. The literature leads to the hypothesis that HIV-1 infection is a battleground in which DCs could be leading both of the armies, the aggressor that promotes HIV-1 replication from relatively small numbers of infected cells and the defender that mediates T cell-dependent resistance.

Infection and apoptotic cell death of CD4+ T cells during an immune response to HIV-1-pulsed dendritic cells

Interacting dendritic cells and helper CD4+ lymphocytes form a microenvironment that is permissive for HIV-1 replication. The virus need only be pulsed initially onto the dendritic cells, which then transfer HIV-1 to the lymphocytes that are responding to presented antigens or superantigens. We have pursued underlying mechanisms in this system, because it provides a model for the infection of antigen-reactive, primary T cells. Pulsing the T cells with HIV-1 results in much less of a subsequent infection than does pulsing the dendritic cells. The latter pulse occurs effectively in the presence of AZT. Direct examination of the interacting dendritic cells and T cells reveals extensive production of p24 by many of the lymphocytes, including syncytia. The majority of the responding T cells die during the coculture. Apoptosis accounts for much of this death as revealed by in situ nick translation assays for DNA endonucleolysis, and hypodiploid profiles on staining with DNA-binding dyes. Therefore the microenvironment that is generated between antigen-presenting dendritic cells and T cells reveals the cytopathic potential of HIV-1, because there is such extensive and rapid death by apoptosis of antigen-reactive T cells.

Strain measurement in the medial collateral ligament of the human knee: an autopsy study

A strain transducer was developed which employs a magnetic field sensing device to detect linear displacement. The transducer was attached to the medial collateral ligament (MCL) of human autopsy specimens, minimally influencing their physiologic behavior. A strain 'map' of the MCL as a function of knee flexion (full extension to 120 degrees) both with and without abduction force was obtained. Our investigation revealed consistent differences in the strain patterns between proximal, middle and distal segments of the anterior and posterior borders of the MCL. Anatomic variations in the pattern of collagen fibers within the MCL, interactions between posterior oblique capsular fibers and the MCL, and the skeletal configuration may account for these varied strain patterns.

A technique for needle localization in paraspinal muscles with cadaveric confirmation

Invasive electromyography (EMG) of the paraspinal muscles is useful in clinical and research settings. No technique for localization of the needle in specific fascicles has been validated. Recent descriptions of the segmented innervation of the multifidus imply that such a technique would add greatly to the EMG determination of root level of a radiculopathy. We have developed a technique for localization which relies on palpation of bony structures and needle insertion at certain angles and depths. The technique was evaluated by injecting latex dye in 199 locations in 13 cadavers. Dissection demonstrated that the technique was accurate in 91 of 112 injections into specific fascicles of the multifidus (originating from different spinous processes), 39 of 43 injections into the longissimus, and 35 of 44 injections into the iliocostalis. Certain types of errors would not have occurred with the aid of EMG in vivo. When these are added to the correct injections, accuracy improves 97%, 93%, and 82%, respectively. The technique described here should be useful for kinesiological studies, biopsies and injections, as well as for the EMG confirmation of a radiculopathy.

Both dendritic cells and memory T lymphocytes emigrate from organ cultures of human skin and form distinctive dendritic-T-cell conjugates

Prior studies of mouse skin in organ culture have shown that dendritic cells selectively emigrate from the explants over 1-3 d. This emigration may model the movements of dendritic cells that can occur in situ, as in transplantation and contact sensitivity. In this study, we cultured explants of normal human skin that had been removed with a dermatome. Dendritic cells with characteristic morphology and mixed leukocyte response-stimulatory activity emigrated. The dendritic cells had the expected phenotype, e.g., rich in major histocompatibility complex class II and accessory molecules such as B7-1, intercellular adhesion molecule-1, and leukocyte function-associated antigen-3. Small lymphocytes also were present in the emigrated populations and proved to be T cells exclusively, almost entirely of the TcR alpha beta and memory type (CD45RAweak, CD45RO LFA-3/CD58+), with a CD4:CD8 subset ratio of about 2:1. Some of the T cells were bound tightly to the dendritic cells. These conjugates did not dissociate after exposure to trypsin or to calcium- and magnesium-free medium, or during cytofluorography. This made it possible to sort distinct populations of single dendritic cells, single T cells, and conjugates of the two cell types. Conjugates would continue to form from mixtures of separated dendritic cells and T cells in culture. Therefore, cutaneous dendritic cells and memory T lymphocytes emigrate from human skin explants, and some of these cells form distinctive conjugates that we hypothesize contribute to immunologic recall reactions.