Modulation of intestinal cholesterol absorption by high glucose levels: impact on cholesterol transporters, regulatory enzymes, and transcription factors.

Growing evidence suggests that the small intestine may contribute to excessive postprandial lipemia, which is highly prevalent in insulin-resistant/Type 2 diabetic individuals and substantially increases the risk of cardiovascular disease. The aim of the present study was to determine the role of high glucose levels on intestinal cholesterol absorption, cholesterol transporter expression, enzymes controlling cholesterol homeostasis, and the status of transcription factors. To this end, we employed highly differentiated and polarized cells (20 days of culture), plated on permeable polycarbonate filters. In the presence of [(14)C]cholesterol, glucose at 25 mM stimulated cholesterol uptake compared with Caco-2/15 cells supplemented with 5 mM glucose (P < 0.04). Because combination of 5 mM glucose with 20 mM of the structurally related mannitol or sorbitol did not change cholesterol uptake, we conclude that extracellular glucose concentration is uniquely involved in the regulation of intestinal cholesterol transport. The high concentration of glucose enhanced the protein expression of the critical cholesterol transporter NPC1L1 and that of CD36 (P < 0.02) and concomitantly decreased SR-BI protein mass (P < 0.02). No significant changes were observed in the protein expression of ABCA1 and ABCG8, which act as efflux pumps favoring cholesterol export out of absorptive cells. At the same time, 3-hydroxy-3-methylglutaryl-coenzyme A reductase activity was decreased (P < 0.007), whereas ACAT activity remained unchanged. Finally, increases were noted in the transcription factors LXR-alpha, LXR-beta, PPAR-beta, and PPAR-gamma along with a drop in the protein expression of SREBP-2. Collectively, our data indicate that glucose at high concentrations may regulate intestinal cholesterol transport and metabolism in Caco-2/15 cells, thus suggesting a potential influence on the cholesterol absorption process in Type 2 diabetes.

Antibody response to a two-dose regimen of influenza vaccine in allogeneic T cell-depleted and autologous BMT recipients.

Induction of protective hemagglutination-inhibition (HI) antibodies in response to influenza virus vaccine and the effectiveness of two doses versus a single dose of vaccine were studied in 48 BMT recipients. The patients were 1-50 years old (median 21 years), 33 with malignant and 15 with non-malignant disease. Thirty-five of the patients underwent allogeneic, T lymphocyte-depleted, BMT and 13, autologous BMT. Nine patients had GVHD at initial immunization. The time interval from BMT to influenza vaccination ranged from 2 to 82 months (median 14.5 months). Two doses of vaccine, administered 1 month apart, consisted of trivalent influenza subunit inactivated vaccine with the following strains: A/Singapore/6/86 (H1N1), A/Sichuan/2/87 (H3N2), and B/Beijing/1/87. There was a statistically significant association between development of protective antibody level (> or = 1:40) and the time interval between BMT and initial vaccination (p < or = 0.001). Regression analysis revealed that longer time interval between the BMT and immunization was positively correlated with seroconversion (a fourfold or greater rise in titers). In the presence of GVHD, there was reduced seroconversion to H1N1, but not to H3N2 or B strains. Influenza vaccination within the first 6 months following BMT was totally ineffective. The efficacy of the vaccine was similar to that described in non-immunocompromised hosts initiated 2 years following BMT. As, overall, specific response was only marginally enhanced by the second dose of vaccine, its indication is questionable.

Detection of herpes simplex virus in gingival tissue.

The presence of herpes simplex virus (HSV) antigens was shown by immunofluorescence staining in 26 of 66 (39.3%) specimens of clinically healthy gingiva, but only one sample contained infectious virus. HSV DNA sequences were clearly identified in intact gingival cells by dot blot hybridization in one specimen, and a weak pattern in a second one. Both specimens harbored viral antigens. These findings of viral genome and protein expression suggest that the virus is present in the latent form in the gingiva.

Detection of human cytomegalovirus DNA in human tonsillar lymphocytes.

The human cytomegalovirus (HCMV) was first isolated in cell cultures from the oropharynx, which is thought to be a site of primary infection. Although HCMV can be recovered from the oropharynx during reactivation phases, its exact site of latency is not known. In the present study we demonstrated evidence suggesting the presence of latent HCMV in this anatomic region--in the palatine tonsils. Samples from 30 tonsils obtained by tonsillectomy were screened for the presence of HCMV. Out of the 30 tonsil donors, 23 were seropositive for HCMV. Three methods were used in attempts to demonstrate HCMV's presence in the tonsils: (1) viral isolation attempts on various cell cultures, (2) immunohistochemical staining--immunoperoxidase method--designed to detect viral antigens, and (3) DNA dot hybridization with a HCMV-DNA probe designed to detect viral DNA. Neither infectious HCMV nor other viruses were isolated in cell cultures. No viral antigens were detected by immunoperoxidase staining in the tonsillar tissue. Four out of the 30 tonsils studied were found to contain viral DNA. In one case in which the tonsillar mononuclear (MN) fraction was separated from the polymorphonuclear (PMN) fraction, only the first fraction contained the viral DNA.

An immunoperoxidase study of cytomegalovirus mononucleosis.

Indirect immunoperoxidase method was used to evaluate retrospectively a case of cytomegalovirus (CMV) mononucleosis. Specific rabbit antiserum against CMV was used as primary reagent in routinely prepared paraffin sections of lymph node and in fixed slide preparations of the bone marrow aspirate. Staining specific for CMV antigen was observed in the lymphoid cells of the lymph node in the predominantly T-cell area and in the large lymphoid cells of the bone marrow. Bone marrow lymphoid cells with morphologic characteristics similar to those of the cells positive for CMV antigen showed positive immunoperoxidase reaction with specific rabbit antihuman T-cell serum. The data strongly indicate that CMV antigen was localized predominantly in the cells of lymphoid origin during the acute stage of the CMV mononucleosis; some data also suggest that infected lymphoid cells may be of T-cell origin. An immunoperoxidase technique is advantageous in both diagnosing and evaluating CMV mononucleosis.

Prolonged atypical illness associated with serological evidence of persistent Epstein-Barr virus infection.

Seven patients with prolonged atypical illness were followed up for more than a year. Sera taken during that period showed significantly increased titres of IgM antibodies against the viral capsid antigen (VCA) of Epstein-Barr virus (EBV). In four of the patients antibodies to the R component of the early antigen (EA) complex of EBV were clearly detectable. Only one of these seven patients had presented with symptoms of classic infectious mononucleosis. Serological and clinical observations in these patients suggest that the prolonged atypical illness was probably the result of persistent EBV infection.

Antibodies to human T lymphocytes in xenoantisera elicited with a new immature T-cell line (Peer).

Peer, a continuous line of immature T lymphocytes, was recently established from a patient with T-cell leukemia. In the present study antisera elicited in rabbits by immunization with Peer cells and absorbed with B cells were found to react with a distinct T-lymphocyte antigen. Absorbed anti-Peer serum was highly cytotoxic for human thymus cells and exerted a preferential activity on peripheral T lymphocytes. Peripheral blood lymphocytes (PBL) surviving exposure to anti-Peer serum and complement were depleted of most of the cells forming E rosettes, whereas the proportion forming EAC' rosettes was increased. Similarly, the depletion of cells forming E rosettes resulted in a concomitant reduction of the sensitivity of PBL to the cytotoxic effect of anti-Peer serum, while the enrichment of E-rosette forming cells had the opposite effect. Anti-Peer serum did not inhibit the formation of E rosettes by PBL in the absence of complement. Absorbed anti-Peer serum failed to exert any cytotoxic effect not only on normal B lymphocytes but also on the CBL and IMB B-cell lines, yet maintained a cytotoxic activity on the Raji and Daudi cell lines. A possible interpretation of these results is that immunization with Peer cells, a line of immature T lymphocytes, leads to the production of antibodies to a distinct antigen expressed on thymus and peripheral T cells. The antigen seems to be absent from normal peripheral B lymphocytes, but may be expressed on a line of pre-B cells, such as the Raji and Daudi lines.

Establishment and characterization of a new leukaemic T-cell line (Peer) with an unusual phenotype.

We report the isolation and establishment in continuous culture of a human lymphoid cell line (Peer) from a case of T-leukemia. The Peer cell line lacks some typical cell-surface properties of T cells, namely sheep erythrocyte rosette formation and reactivity with two anti-T-cell sera, but has focal acid phosphatase and does express two other T-cell antigens, one defined by a monoclonal antibody, the other related to a T-cell subset (TH2). The cells are negative for B-cell markers (SmIg or cytoplasmic mu Fcgamma and C3 receptors, mouse erythrocyte rosettes) and EBV (EBNA). In addition, the Peer cell does not possess the typical phenotypic markers of "non-B, non-T" leukemia: cALL and Ia-like antigens, and the cytoplasmic hexosaminidase isoenzyme I, but is positive for terminal deoxynucleotidyl transferase by enzymatic and immunofluorescent criteria. The cell line requires exogenous L-asparagine for adequate growth in culture, a property known to be characteristic of certain T cells but not of B cells. The Peer cell line appears to have a maturation arrest at a developmental stage intermediate between the cortical thymocyte and a mature T-cell subset and to have lost some T-cell differentiation features.