Human Epidermal Langerhans Cells and Peripheral Blood Monocytes

We compared the functional capacities of human epidermal Langerhans cells (LC) and peripheral blood monocytes. Epidermal sheets were obtained by a suction blister device. After enzymatic treatment LC were enriched by attaching them to IgG-located erythrocyte monolayers. On a per cell basis, LC were several times more efficient accessory cells than monocytes in augmenting nickel-and tuberculin (PPD)-induced T-cell proliferation. In mixed cell cultures LC stimulated both autologous and allogeneic T cells, whereas monocytes stimulated only allogeneic cells. In addition, LC were significantly more potent allogeneic stimulators than monocytes. Although monocytes were weaker accessory cells and allogeneic stimulators than LC, they induced higher interleukin 1 (IL-1) activities than LC-enriched or LC-depleted cells. These results indicate that there are functional differences between LC and monocytes and that antigen presentation and mediator secretion are not correlated.     

Porphyromonas gingivalis Outer Membrane Vesicles Enter Human Epithelial Cells via an Endocytic Pathway and Are Sorted to Lysosomal Compartments

Porphyromonas gingivalis, a periodontal pathogen, secretes outer membrane vesicles (MVs) that contain major virulence factors, including major fimbriae and proteases termed gingipains, although it is not confirmed whether MVs enter host cells. In this study, we analyzed the mechanisms involved in the interactions of P. gingivalis MVs with human epithelial cells. Our results showed that MVs swiftly adhered to HeLa and immortalized human gingival epithelial cells in a fimbria-dependent manner and then entered via a lipid raft-dependent endocytic pathway. The intracellular MVs were subsequently routed to early endosome antigen 1-associated compartments and then were sorted to lysosomal compartments within 90 min, suggesting that intracellular MVs were ultimately degraded by the cellular digestive machinery. However, P. gingivalis MVs remained there for over 24 h and significantly induced acidified compartment formation after being taken up by the cellular digestive machinery. In addition, MV entry was shown to be mediated by a novel pathway for transmission of bacterial products into host cells, a Rac1-regulated pinocytic pathway that is independent of caveolin, dynamin, and clathrin. Our findings indicate that P. gingivalis MVs efficiently enter host cells via an endocytic pathway and survive within the endocyte organelles for an extended period, which provides better understanding of the role of MVs in the etiology of periodontitis.Outer membrane vesicles (MVs), ubiquitously shed from gram-negative bacteria by a mechanism involving cell wall turnover, consist of outer membrane lipids, as well as a subset of outer membrane proteins and soluble periplasmic components (56). Gram-negative pathogens have developed type I to VII secretion systems to transport active virulence factors in an extracellular manner (16, 49). Delivery by MVs is thought to be a distinct typeable secretion system that may play a part in the strategy utilized by bacterial pathogens to establish a colonization niche, modulate host defense and response, and impair host cell function. Thus, MVs have been proposed to be natural vehicles, or bacterial “bombs” (26). MVs from pathogenic strains such as Pseudomonas aeruginosa (2), Helicobacter pylori (18), and Actinobacillus actinomycetemcomitans (8), as well as pathogenic and nonpathogenic Escherichia coli (7, 53), have been shown to contain various active virulence factors such as toxins, proteases, adhesins, and lipopolysaccharide. However, the molecular mechanism of the entry of MVs into host cells for virulence factor delivery is largely unknown. Recently, cellular entry by MVs derived from enterotoxigenic E. coli was closely analyzed (24). Those results showed that the MVs were taken up by a human epithelial cell line via lipid rafts, which was dependent on monosialoganglioside and intracellular MVs accumulated in nonacidified compartments inaccessible to the extracellular milieu. Thus, it was concluded that enterotoxigenic E. coli MVs function as specifically targeted transport vehicles that mediate entry of heat-labile enterotoxin and other bacterial envelope components into host cells. These findings suggest a novel mechanism for bacterial virulence factor transmission into host cells, although no other related results have been reported.Periodontitis, one of the most common infectious diseases seen in humans (54), is characterized by gingival inflammation, as well as loss of connective tissue and bone from around the roots of the teeth, which leads to eventual tooth exfoliation. This infectious disorder is caused by a small subset of periodontal gram-negative anaerobic bacteria (17). Among those, Porphyromonas gingivalis is considered to be a bona fide pathogen that causes several forms of severe periodontal disease, and has also been reported to contribute to systemic conditions such as cardiovascular diseases (34) and preterm low birth weight (38). P. gingivalis releases MVs in an extracellular manner, which retain the full components of outer membrane constituents, including lipopolysaccharide, muramic acid, a capsule, fimbriae, and proteases termed “gingipains” (13, 33). Long fimbriae (referred to herein as simply fimbriae) reportedly mediate bacterial adherence to and entry into periodontal cells (1), while gingipains contribute to the destruction of periodontal tissues (20). Therefore, fimbriae and gingipains provide adhesive and proteolytic abilities to MVs, which, together with their small size (20 to 500 nm), are suspected to enable them to penetrate intact mucosa and enter underlying host tissues and cells (32). However, the mechanisms involved in the interactions of P. gingivalis MVs with the host cell remain unknown, and no study has actually demonstrated that MVs adhere to or enter host cells. Thus, we considered it important to determine how P. gingivalis MVs are taken up by human epithelial cells, as well as whether intracellular MVs are sorted to lytic compartments or accumulate in nonacidified compartments as enterotoxigenic E. coli MVs.In the present study, we performed molecular dissection to elucidate the mechanisms underlying entry into and intracellular trafficking of P. gingivalis MVs in human cervical HeLa and immortalized human gingival epithelial (IHGE) cells.     

Attachment of Cryptosporidium parvum Sporozoites to Human Intestinal Epithelial Cells

An enzyme-linked immunosorbent assay-based attachment model using the human intestinal cell line Caco-2A was developed to study attachment of Cryptosporidium parvum sporozoites in vitro and to assess potential inhibitors of sporozoite binding. In this system, attachment was related to sporozoite dose, incubation time, and host cell differentiation status. Polyclonal antibodies to C. parvum as well as glycoprotein inhibitors of a sporozoite lectin reduced attachment. This model will be a valuable tool in elucidating specific molecules and mechanisms involved in sporozoite-host cell attachment.     

Role of ELAM-1 in Adhesion of Monocytes to Activated Human Endothelial Cells

The role of ELAM-1 in the adhesion of monocytes to HUVEC, activated for 4h with TNF, was studied using MoAb ENA2 directed against ELAM-1. In a standard adhesion assay at 37 degrees C, F(ab')2 fragments of ENA2 did not, or weakly inhibited adhesion. When metabolic activity of the monocytes was reduced by (i) fixing the monocytes, (ii) performing the adhesion assay at 4 degrees C, and (iii) combining the forementioned conditions, the adhesion of the monocytes was strongly blocked by ENA2 and less effective or not by MoAb IB4 anti-CD18. The pattern of adhesion of monocytes to HUVEC, activated with TNF assessed at 4 degrees C, paralleled ELAM-1 expression on the endothelial cells. Maximal inhibitory effect of ENA2 on adhesion was shown 5 h after activation of HUVEC, at which ELAM-1 expression was also maximal. Adhesion assessed at 37 degrees C remained enhanced for at least 24 h, whereas the inhibitory effect of ENA2 followed ELAM-1 expression. Specific involvement of ELAM-1 was also confirmed using ELAM-1 transfected COS cells. These results indicated that monocytes express a counter structure for ELAM-1 and that this counter structure is involved in adhesion.     

Streptococcus pneumoniae Impairs Maturation of Human Dendritic Cells and Consequent Activation of CD4+ T Cells via Pneumolysin

Influenza A Virus (IAV), Staphylococcus aureus (staphylococci), and Streptococcus pneumoniae (pneumococci) are leading viral and bacterial causes of pneumonia. Dendritic cells (DCs) are present in the lower respiratory tract. They are characterized by low expression of co-stimulatory molecules, including CD80 and CD86 and high capacity of antigen uptake. Subsequently, DCs upregulate co-stimulatory signals and cytokine secretion to effectively induce T-cell priming. Here, we investigated these processes in response to bacterial and viral single as well as coinfections using human monocyte-derived (mo)DCs. Irrespective of single or coinfections, moDCs matured in response to IAV and/or staphylococcal infections, secreted a wide range of cytokines, and activated CD4⁺, CD8⁺ as well as double-negative T cells. In contrast, pneumococcal single and coinfections impaired moDC maturation, which was characterized by low expression of CD80 and CD86, downregulated expression of CD40, and a mild cytokine release resulting in abrogated CD4⁺ T-cell activation. These actions were attributed to the cholesterol-dependent cytotoxin pneumolysin (Ply). Infections with a ply-deficient mutant resulted in restored moDC maturation and exclusive CD4⁺ T-cell activation. These findings show that Ply has important immunomodulatory functions, supporting further investigations in specific modalities of Ply-DC interplay.     

Differential Sensitivity of Human Epithelial Cells to Pseudomonas aeruginosa Exoenzyme S

Exoenzyme S (ExoS) is an ADP-ribosyltransferase produced and directly translocated into eukaryotic cells by the opportunistic pathogen Pseudomonas aeruginosa. Model systems that allow bacterial translocation of ExoS have found ExoS to have multiple effects on eukaryotic cell function, affecting DNA synthesis, actin cytoskeletal structure, and cell matrix adherence. To understand mechanisms underlying differences observed in cell sensitivities to ExoS, we examined the effects of bacterially translocated ExoS on multiple human epithelial cell lines. Of the cell lines examined, confluent normal kidney (NK) epithelial cells were most resistant to ExoS, while tumor-derived cell lines were highly sensitive to ExoS. Analysis of the mechanisms of resistance indicated that cell association as well as an intrinsic resistance to morphological alterations were associated with increased resistance to ExoS. Conversely, increased sensitivity to ExoS appeared to be linked to epithelial cell growth, with tumor cells capable of undergoing non-contact-inhibited, anchorage-independent growth all being sensitive to ExoS, and NK cells becoming sensitive to ExoS when subconfluent and growing. Consistent with the possibility that growth-related, actin-based structures are involved in sensitivity to ExoS, scanning electron microscopy revealed cellular extensions from sensitive, growing cells to bacteria, which were not readily evident in resistant cells. In all studies, the severity of effects of ExoS on cell function directly correlated with the degree of Ras modification, indicating that sensitivity to ExoS in some manner related to the efficiency of ExoS translocation and its ADP-ribosylation of Ras. Our results suggest that factors expressed by growing epithelial cells are required for the bacterial contact-dependent translocation of ExoS; as normal epithelial cells differentiate into polarized confluent monolayers, expression of these factors is altered, and cells in turn become more resistant to the effects of ExoS.     

New Isolation Technique to Study Apoptosis in Human Intestinal Epithelial Cells

Intestinal epithelial cells derive from stem cells at the base of the crypt and migrate along the crypt-lumen axis. Their life is terminated as they reach the luminal surface where they detach and are shed. Intestinal epithelial cells show evidence of apoptosis in the region of shedding, and cell death is thought to resemble a form of apoptosis called detachment-induced cell death, or anoikis. Human intestinal epithelial cells die rapidly in vitro due to loss of anchorage during isolation, making primary culture of these cells a goal that has not yet been reached. However, the molecular mechanisms underlying this process of anoikis are largely unknown. In this study, a novel protocol for the rapid, temperature-controlled isolation of highly purified human colonic epithelial cells from surgical specimens is described. Using this method, early molecular events of anoikis in nontransformed epithelial cells were studied. Intestinal epithelial cells were isolated at the beginning of the apoptotic cascade, before the activation of caspase 3 family members and cleavage of poly(ADP-ribose) polymerase and DNA fragmentation. Elucidating the molecular mechanisms of detachment-induced cell death may facilitate the establishment of long-term primary cultures of human intestinal epithelial cells and enhance our understanding of homeostasis in the intestinal epithelium.     

Adherence of Human Vaginal Lactobacilli to Vaginal Epithelial Cells and Interaction with Uropathogens

Three strains of Lactobacillus, identified as Lactobacillus acidophilus, Lactobacillus gasseri, and Lactobacillus jensenii, were selected from among 70 isolates from the vaginas of healthy premenopausal women for properties relevant to mucosal colonization or antagonism. All three self-aggregated and adhered to epithelial vaginal cells, displacing well-known vaginal pathogens, such as G. vaginalis, and inhibiting the growth in vitro of Escherichia coli and Streptococcus agalactiae. The surface components involved in self-aggregation appeared to be proteins for L. gasseri and lipoproteins for L. acidophilus and L. jensenii, as judged by susceptibility to treatment with appropriate degrading enzymes. The factors responsible for adherence to epithelial vaginal cells seemed to be glycoproteins (L. acidophilus and L. gasseri) and carbohydrate (L. jensenii). The receptors of the vaginal cells were glycolipids, which presumably were the targets of the competition observed between the lactobacilli and the pathogenic microbes.     

Destruction of Dextran-Coated Target Cells by Normal Human Lymphocytes and Monocytes.

A human anti-dextran serum, EAK, with IgG antibodies restricted to subclass IgG2, was tested for its capacity to induce lysis of dextran-coated chicken erythrocytes by normal human lymphocytes or monocytes. Another human anti-dextran serum, RGM, with most antibodies belonging to sublass IgG1, and a hyperimmune rabbit anti-dextran serum were used for reference. In lymphocyte-mediated erythrolysis, serum EAK gave rise to 51-Cr release varying from 20% to 80% in different experiments. The hyperimmune rabbit serum was 100 to 1000 times more active, whereas serum RGM was consistently negative. These results correlated well with the concentration of anti-dextran antibodies in these sera. In monocyte-mediated erythrolysis serum EAK had a somewhat higher titer than in lymphocyte-mediated lysis, and serum RGM had a weak but significant activity at low dilutions. Serum EAK also induced erythrophagocytosis by monocytes. Ultracentrifugation did not significantly decrease the inductive capacity of this serum. The results show that antibodies of human sublass IgG2 are efficient inducers of effector functions in both lymphocytic and monocytic cells. Myeloma proteins of the four IgG subclasses were tested for inhibitory capacity in lymphocyte- or monocyte-mediated erythrolysis. Either serum EAK or the rabbit reference serum was used for induction of erythrolysis. Individual myeloma proteins within and between the subclasses varied considerably in inhibitory power. However, whereas IgG1, IgG2, and IgG3 proteins inhibited lymphocyte-mediated erythrolysis induced by either type of antiserum, the two IgG4 proteins tested were essentially negative. These results suggest a lack of specificity of the Fc receptor for subclasses IgG1, IgG2, and IgG3 in both heterologous and homologous inhibition. In monocyte-mediated erythrolysis, IgG1 and IgG3 were strong inhibitors, whereas inhibition by IgG2 and IgG4 was weak and inconsistent. This pattern was seen regardless of whether and inducing antiserum was of rabbit or human origin. Similar results were obtained in monocyte-induced erythrophagocytosis induced by serum EAK. These and previous results suggest that effector cells of the lymphocytic (K cell) variety have Fc receptors different from those of monocytic cells. However, the basis for the differences observed in the inhibition tests remains to be elucidated.     

Salmonella typhi Flagella Are Potent Inducers of Proinflammatory Cytokine Secretion by Human Monocytes

The cytokine production patterns of human peripheral blood mononuclear cells (PBMC) in response to Salmonella typhi flagella (STF) were examined in culture supernatants of PBMC stimulated with STF. Consistent with previous findings in volunteers vaccinated with aroC aroD deletion mutants of S. typhi, PBMC from volunteers immunized with the licensed live Ty21a S. typhi vaccine secreted gamma interferon following exposure to STF. Stimulation with STF induced rapid de novo synthesis of tumor necrosis factor alpha (TNF-alpha) and interleukin-1beta (IL-1beta), followed by IL-6 and IL-10. Trypsin treatment of STF abrogated their effects, while polymyxin B had no effect. Intracellular cytokine measurements of STF-stimulated PBMC revealed the existence of monocyte subpopulations that produce only TNF-alpha, IL-1beta or both cytokines. Moreover, STF markedly decreased the percentage of CD14(+) cells. These data demonstrate that STF are powerful monocyte activators which may have important implications for vaccine development and for understanding the pathogenesis of S. typhi infection.     

Inhibition of Pneumococcal Adherence to Human Nasopharyngeal Epithelial Cells by Anti-PsaA Antibodies

The role of pneumococcal (Pnc) surface adhesin A (PsaA) in the adherence of Streptococcus pneumoniae (pneumococcus) to host cells is not well defined. We examined the effect of anti-PsaA antibodies in an inhibition of adherence assay using Detroit 562 nasopharyngeal human epithelial cells. Rabbit polyclonal (Pab) anti-recombinant PsaA (rPsaA) sera, a purified mouse monoclonal antibody (MAb) (MAb 6F62G8E12), and 22 healthy adult sera with known anti-PsaA IgG levels (obtained by enzyme-linked immunosorbent assay) were evaluated for their abilities to inhibit Pnc adherence to confluent monolayers (measured as percent reduction in CFU counts compared to those of uninhibited controls). Pnc adherence was dependent on capsular phenotype (no or low adherence for opaque strains). With an inoculum of 10⁴ to 10⁵ bacteria/well, the mean ± standard deviation count in controls was 163 ± 32 CFU/well for transparent strains. Low adherence was observed for a PsaA-minus mutant even at higher inoculum doses. Mean percent inhibitions of adherence with Pab and MAb were 54 and 50%, respectively. Adult sera showed inhibition in a dose-response fashion with a range of 98 to 8%, depending on the serum anti-PsaA antibody concentration. Absorption of Pab with rPsaA restored Pnc adherence to control levels. Absorption of sera with a PsaA-minus mutant did not result in a significant decrease (P >0.05) of inhibition of adherence activity. Additionally, nearly 100% of Pnc adherence was inhibited by lipidated rPsaA at 2.5 μg/ml. Our data support the argument that PsaA is an adhesin that mediates Pnc adherence to human nasopharyngeal cells. This functional assay may be useful in evaluating antibodies elicited in response to PsaA vaccination.     

Epithelial Cells Infected with Chlamydophila pneumoniae (Chlamydia pneumoniae) Are Resistant to Apoptosis

The obligate intracellular pathogen Chlamydophila pneumoniae (Chlamydia pneumoniae) initiates infections in humans via the mucosal epithelia of the respiratory tract. Here, we report that epithelial cells infected with C. pneumoniae are resistant to apoptosis induced by treatment with drugs or by death receptor ligation. The induction of protection from apoptosis depended on the infection conditions since only cells containing large inclusions were protected. The underlying mechanism of infection-induced apoptosis resistance probably involves mitochondria, the major integrators of apoptotic signaling. In the infected cells, mitochondria did not respond to apoptotic stimuli by the release of apoptogenic factors required for the activation of caspases. Consequently, active caspase-3 was absent in infected cells. Our data suggest a direct modulation of apoptotic pathways in epithelial cells by C. pneumoniae.     

Invasion of Human Oral Epithelial Cells by Prevotella intermedia

Invasion of oral epithelial cells by pathogenic oral bacteria may represent an important virulence factor in the progression of periodontal disease. Here we report that a clinical isolate of Prevotella intermedia, strain 17, was found to invade a human oral epithelial cell line (KB), whereas P. intermedia 27, another clinical isolate, and P. intermedia 25611, the type strain, were not found to invade the cell line. Invasion was quantified by the recovery of viable bacteria following a standard antibiotic protection assay and observed by electron microscopy. Cytochalasin D, cycloheximide, monodansylcadaverine, and low temperature (4°C) inhibited the internalization of P. intermedia 17. Antibodies raised against P. intermedia type C fimbriae and against whole cells inhibited invasion, but the anti-type-C-fimbria antibody inhibited invasion to a greater extent than the anti-whole-cell antibody. This work provides evidence that at least one strain of P. intermedia can invade an oral epithelial cell line and that the type C fimbriae and a cytoskeletal rearrangement are required for this invasion.     

人血单核细胞和U937细胞产生IFN-α的比较

一般认为人体单核-巨噬细胞(Mo-Mφ)系在体外诱生IFN-α较为困难,本文试图找到适合的培养条件,使Mo-M(?)系能在体外诱生IFN-α.结果显示:经M-CSF长期预处理和IFN-γ的短期预处理或单用IFN-γ短期预处理后,NDV刺激均能使人外周血Mo-M(?)产生较高水平的IFN-α;U937细胞只能产生低水平的IFN-α.     

A and B Antigenicity of Human Spermatozoa and Buccal Epithelial Cells

The source of A and B antigens on the surface of erythrocytes, spermatozoa and buccal epithelial cells was studied using two kinds of monoclonal antibodies of differing specificity. The first, anti-Ar, reacts with the erythrocyte A antigen but not with the soluble A antigen found in secretions such as saliva. Similarly, anti-Br reacts with the erythrocyte B antigen but not with the soluble B antigen present in secretions. The second type of monoclonal antibody, anti-A_r+s, reacts with both the erythrocyte A antigen and with the soluble A blood group substance. Similarly, the anti-B_r+s reacts with both the erythrocyte B antigen and with the soluble B blood group substance. The spermatozoal A antigen reacts only with the anti-A_r+s monoclonal antibody whereas buccal epithelial A antigen reacts with both anti-A_r and with anti-A_r+s. Spermatozoal B antigen reacts only with anti-B_r+s whereas buccal epithelial B antigen reacts with both anti-B_r and anti-B_r+s. Buccal cell A and B antigens appear to be integral to the membrane or at least tightly bound whereas the spermatozoal A and B antigens are adsorbed from seminal plasma and loosely bound.     

Adherence of Lysostaphin to and Penetration into Human Monocytes

The effect of lysostaphin on Staphylococcus aureus phagocytosed by monocytes was investigated. The results showed that lysostaphin adheres to monocytes by a temperature-independent mechanism, is not adequately removed from monocytes by washing, and penetrates by means of a temperature-dependent mechanism. In in vitro assays of monocyte function, phagocytosed S. aureus can be killed by lysostaphin after penetration of the cells during incubation or by adhering lysostaphin when the monocytes are disrupted.     

Biliary Epithelial Cells Are Not the Predominant Source of Hepatic CXCL12

Hepatic expression levels of CXCL12, a chemokine important in inflammatory and stem cell recruitment, and its receptor, C-X-C chemokine receptor 4, are increased during all forms of liver injury. CXCL12 is expressed by both parenchymal and nonparenchymal hepatic cells, and on the basis of immunohistochemistry, biliary epithelial cells (BECs) are thought to be a predominant source of hepatic CXCL12, thereby promoting periportal recruitment of C-X-C chemokine receptor 4–expressing lymphocytes. Our study aims to show that BECs may, in fact, not be the predominant source of hepatic CXCL12. We measured CXCL12 secretion and expression from human and murine BECs using enzyme-linked immunosorbent assay and Western blot analysis from cell culture supernatants and whole cell lysates, respectively, whereas CXCL12 expression in murine livers was analyzed in a Cxcl12-Gfp reporter mouse. Cell culture supernatants and whole cell lysates from BECs failed to demonstrate their expression of CXCL12. Furthermore, we confirmed these results with a Cxcl12-Gfp reporter mouse in which green fluorescent protein expression is notably absent from BECs. Interestingly, on the basis of green fluorescent protein expression, we demonstrate a population of CXCL12-expressing cells within the portal tract that are distinct, yet intimately associated with BECs. These findings indicate that BECs are not a predominant source of CXCL12.CXCL12, a chemokine important in hematopoietic stem cell homeostasis, and its receptor, C-X-C chemokine receptor 4 (CXCR4), are up-regulated in many disease pathologies and promote inflammation and tumor metastasis.¹ Specifically, in patients with liver disease, CXCL12 expression is increased in both serum and hepatic tissue proportional to the extent of injury.² CXCL12 expression has been documented in stellate cells, sinusoidal endothelial cells, and biliary epithelial cells (BECs) and is thought to drive inflammation and fibrogenesis, although its role, particularly in normal liver, remains largely unknown.³ During fetal development, B-cell lymphopoiesis is dependent on hepatic CXCL12,⁴ and in the adult, hepatic CXCL12 may support a hepatic hematopoietic stem cell niche.⁵ Finally, with injury, immunohistochemical data demonstrate robust CXCL12 expression by proliferating bile ductules in all forms of liver injury, and biliary CXCL12 expression is further supported by the accumulation of CXCR4-positive lymphocytes in the periportal region.^2,6A careful review of the literature, however, reveals that most data supporting BEC expression of CXCL12 are based on immunohistochemistry using a single monoclonal CXCL12 antibody (murine anti-human/mouse CXCL12, clone 79018). We believe that differentiated BECs may not express CXCL12 and that the observed pattern of BEC expression is a result of antibody cross-reactivity to an epitope found in BECs. Lack of CXCL12 expression by BECs has previously been alluded to by Mavier et al⁷ using in situ hybridization, where CXCL12 RNA expression in biliary cells lining interlobular bile ducts seemed to be absent. Herein, we show that despite previous studies demonstrating robust CXCL12 expression by BECs, their role in hepatic CXCL12 production may be more limited.^2,6,8     

In Vitro Studies of Human Prostatic Epithelial Cells: Attempts to Identify Distinguishing Features of Malignant Cells

Abstract

Recent advances in culture techniques have enabled routine establishment and propagation of epithelial cells derived from normal and malignant tissues of the human prostate. Comparative studies of the responses of normal and cancer-derived cell populations to various growth and differentiation factors in vitro were undertaken to examine the possibility that cancer cells might respond differentially. Clonal growth assays in serum-free medium demonstrated that optimal proliferation of normal as well as cancer cell strains was generally dependent on the presence of cholera toxin, epidermal growth factor, pituitary extract, hydrocortisone, insulin, and high levels of calcium in the culture medium, and on the use of collagen-coated dishes. Only one cancer strain responded aberrantly to epidermal growth factor and hydrocortisone. Putative differentiation factors (transforming growth factor-β and vitamin A) inhibited the growth of all normal and cancer strains. The origin of a cancer-derived cell strain that responded similarly to normal strains was verified by positive labeling with a prostate cancer-specific antibody, validating the conclusion from these studies that normal and cancer prostatic epithelial cells are not distinguishable on the basis of responses to the tested factors.     

Comparison of Monocytes and B Cells for Activation of Human T Helper Cell Subsets

Human rye grass allergenLol pI-specific T helper cell clones of Thp, Th0, Th1 and Th2 subtype were activated withLol pI and monocytes or B cells as antigen-presenting cells, and cell proliferation, interleukin (IL)-2, interferon-γ, and IL-4 secretion were measured. Monocytes induced activation of T cell clones of all four T helper cell subsets and were usually more potent antigen-presenting cells than B cells. B cells and monocytes similarly induced proliferation and IL-4 secretion by Th2 clones, whereas B cells, in contrast to monocytes, only weakly activated Th1 clones. However, exceptions to this rule existed within each T helper cell subset suggesting that individual T cell clones, regardless of the subset to which they belong, may have quantitatively and/or qualitatively different requirements for secondary activation signals which are provided by the antigen-presenting cells. The data demonstrate that, in general, monocytes are more effective than B cells in activating human T cell clones of all subtypes and that B cells were efficient antigen-presenting cells only for Th2 cells. However, individual T cell clones of any given T helper cell subset vary with respect to their activation by monocytes or B cells.