HIV-1 gp41 shares a common immunologic determinant with human T, B and monocyte cell lines

Several examples of molecular mimicry between HIV-1 and human proteins are reported in the literature. Here we report on yet another example. The monoclonal antibody 3D6 recognized a 17-amino-acid region in HIV-1 gp41 (amino acids 602-618) and could bind to the human T-cell lines H9 and Molt4, B cell lines Raji and Bjab, and monocyte cell lines U937 and HL60. By Western blot using 3D6, a strong band of 43 kDa and a very weak band of 80 kDa were detected in lysates of H9, Molt4, Raji and Bjab cell lines, but only a strong band of 43 kDa was observed in case of U937 and HL60 cells, under reducing or non-reducing conditions. The results indicate the presence of a common immunologic determinant between HIV-1 gp41 and membrane proteins of these human T, B and monocyte cells.

Enhancement of HIV-1 gp41 binding to Raji cells by PWM, LPS, interferon-gamma and interleukin-6

Based on our finding that HIV-1 gp41 independently of CD4 can bind to several proteins (gp41 binding protein: GBP) on the human T-cell line H9, B-cell line Raji and monocyte-cell line U937, we examined the effect of mitogens and cytokines on binding of gp41 to H9, Raji and U937 cells. Flow cytometry (FACS) analysis demonstrated that PWM and LPS, IFN-gamma and IL-6, but not Con A, IFN-alpha, -beta, -omega and IL-2, could increase gp41 binding to Raji cells. In controls, none of the regulators (IFN-alpha, -beta, -gamma, -omega, IL-2, IL-6, Con A, PWM, LPS) could modify the binding potential of H9 and U937 cells. Our data suggest that the expression of HIV-1 binding proteins is subject to regulation by PWM, LPS, IFN-gamma and IL-6 in the case of B-cells, while on T-cells and macrophages, the binding proteins may be constitutively expressed.

HIV-1 gp41 binds to several proteins on the human B-cell line, Raji

Based on our findings that HIV-1 gp41 independently of CD4, can bind to the helper T-cell line H9, we characterized putative binding of HIV-1 gp41 to B-cell lines, Raji, Bjab and Ramos. Using fluorescence-activated cell sorter (FACS) we examined the binding of soluble gp41 (sgp41; Env amino acid 539-684) to these B-cell lines. Using sgp41 attached to sepharose beads Raji cell lysates were absorbed. The sgp41-eluate of Raji cell lysates could inhibit the sgp41-binding to Raji cells. By SDS-PAGE of sgp41-eluate of Raji cell lysates four strong protein band, 37, 45, 49 and 62 kD, and a weak band of 92 kD were stained with Coomassie blue. By Western blot (ligand blot) analysis using sgp41 four protein bands, 37, 45, 49 and 62 kD, were observed in sgp41-eluate of Raji cell lysates. To test the individual proteins the five proteins were isolated from the sgp41-eluate of Raji cell lysates. Three proteins, 45, 49 and 62 kD, each could partially inhibit the sgp41-binding to Raji cells. The results suggest that these three proteins in Raji cell lysates are possible candidates for the putative gp41 receptor(s).

HIV-1 gp41 binding to human peripheral blood mononuclear cells occurs preferentially to B Lymphocytes and monocytes

Based on our findings that HIV-1 gp41 independently of CD4 can bind to the human helper T lymphoid cell line H9, B cell line Raji and monocyte cell line U937, we characterized putative binding of HIV-1 gp41 to human peripheral blood lymphocytes (PBLs) and monocytes. Using flow cytometry (FACS), we demonstrated that the recombinant soluble HIV-1 gp41 (sgp41; Env amino acid 539-684) can bind to the normal human peripheral blood mononuclear cells (PBMCs), preferentially to B lymphocytes and monocytes independently of gp120-binding sites on CD4 molecules. This binding is dose-dependent. The HIV-1 sgp41 binds to blood B lymphocytes and monocytes more strongly than to T lymphocytes. By two-color flow cytometric analysis, we identified that sgp41 can bind 10% of CD4+ T lymphocytes, 11.9% of CD8+ T lymphocytes, 47% of CD19+ B lymphocytes and 44.2% of CD14+ monocytes.

The human monocyte cell line U937 binds HIV-1 gp41 by proteins of 37, 45, 49, 62 and 92 kDa

Based on our findings that HIV-1 gp41 independently of CD4 can bind to the helper T cell line H9 and B cell line Raji, we characterized the putative binding of HIV-1 gp41 to the monocyte cell lines U937 and HL60. Using flow cytometry (FACS) we examined the binding of soluble gp41 (sgp41; env amino acids 539-684) to these monocyte cell lines. Using sgp41 attached to Sepharose beads, U937 cell lysates were absorbed. The sgp41 eluate of U937 cell lysates could inhibit sgp41 binding to U937 cells. With SDS-PAGE of sgp41 eluate of U937 cell lysates, three strong protein bands, (37, 45 and 62 kDa) and two weak bands (49 and 92 kDa) were stained with Coomassie blue. With Western blot (ligand blot) analysis using sgp41, three strong protein bands (37, 49 and 62 kDa) and a very weak band (42-45 kDa) were observed in sgp41 eluate of U937 cell lysates. The results suggest that the four proteins 37, 42-45, 49 and 62 kDa in U937 cell lysates are possible candidates for the putative gp41 receptor(s). We compared the blocking activities of sgp41 eluates from different cell lysates. Not only U937 and Raji lysate-sgp41 eluates, but also H9 and HL60 lysate-sgp41 eluates could block sgp41 binding to U937 and Raji cells. The results indicate that the sgp41-binding proteins on U937, or Raji (H9 and HL60, respectively) probably could have an identical blocking (or binding) specificity; these cell types carry very similar receptor(s) for HIV-1 gp41 binding.

Oral administration of a bacterial immunomodulator enhances murine intestinal lamina propria and Peyer's patch lymphocyte traffic to the lung: possible implications for infectious disease prophylaxis and therapy

LW50020, a bacterial immunomodulator, is a preparation consisting of seven bacteria, commonly causing respiratory disease. When given orally, LW50020 has been shown to enhance the host defense of the respiratory tract. Intestinal lamina propria lymphocytes (LPL), Peyer's patch lymphocytes (PPL), and splenocytes from BALB/c mice gavaged either with LW50020 or carrier alone were isolated, labeled with either H33342, a supravital nuclear fluorochrome, or 51Cr, and injected i.v. into untreated, age-matched BALB/c mice. Two hours later, spleen, liver, lung, kidneys, Peyer's patch, and mesenteric lymph nodes of the recipients were harvested and screened for the presence of labeled cells. LPL from mice gavaged with carrier only (controls) migrated preferentially to the lung, PPL equally well to the lung, and the spleen and splenocytes were found mostly in the spleen. LPL and PPL from LW50020-treated mice were found in significantly larger numbers in the lungs of recipients than LPL and PPL from control animals. Both labeling techniques gave roughly the same results. Sixty-five per cent of LPL in the lung were Thy-1.2+ and 20% B cells. These findings should contribute to the understanding of parameters necessary for the assessment of the mode of action and efficacy of immunomodulation and vaccination via the mucosa-associated lymphoid tissue.

A high-density-lipoprotein receptor appears to mediate the transfer of essential fatty acids from high-density lipoprotein to lymphocytes

It has been shown previously that a specific high-density lipoprotein (HDL) receptor exists on human lymphocytes that recognizes apoprotein (apo) A1 as its ligand, and may be responsible for utilization of HDL lipids to respond optimally to mitogenic stimulation when cultured in serum-free medium supplemented with HDL. To clarify further the relationship between various HDL lipids used by lymphocytes and HDL receptor activity, the lipid composition of the cells and the regulation of HDL and low-density lipoprotein (LDL) receptors on freshly isolated lymphocytes and mitogen-activated T-blasts after treatment with lipoproteins, liposomes or fatty acids were investigated. Our data show that the linear increase in cell proliferation correlates with the presence of HDL in fatty-acid-free culture medium in the concentration range of HDL receptor saturation. Decreased binding/uptake of dioctadecylindocarbocyanine (DiI)-fluorescence-labelled HDL by freshly isolated lymphocytes was observed in the presence of unlabelled HDL in 4-day culture, whereas T-blast binding/uptake was down-regulated by preincubation not only with HDL but also with LDL. T-blasts pretreated with HDL showed increased cellular contents of phosphatidylcholine, oleic acid (C18:1,n-9) and linoleic acid (C18:2,n-6), which are essential for optimal proliferation of mitogen-stimulated lymphocytes. Furthermore, DiI-HDL binding on lymphocytes was down-regulated by up to 20% (resting T cells) and 50% (T-blasts) when cultured in the presence of apoA1-phosphatidylcholine liposomes (T-blasts only), oleic acid or linoleic acid, but not by stearic acid (C18:0). The results indicate that HDL provide lymphocytes with essential fatty acids, which in turn regulate HDL receptor activity.

Lipid utilization by human lymphocytes is correlated with high-density-lipoprotein binding site activity

The nature and physiological importance of high-density lipoprotein (HDL) binding sites on unstimulated (resting) and mitogen-activated (blast) human peripheral blood lymphocytes were investigated. Specific HDL binding on resting and blast T-lymphocytes was saturable at 50 micrograms of 125I-HDL/ml and of high affinity, with Kd values of 8.1 x 10(-8) M and 6.5 x 10(-8) M, respectively, and Bmax. values of 79 ng and 180 ng/mg of cell protein respectively at 4 degrees C. Binding of HDL double-labelled with fluorescent dioctadecylindocarbocyanine (Dil) and isotope (125I) as well as of single fluorescence- or isotope-labelled HDL was inhibited competitively by HDL apoproteins. Studies of the cholesterol flux between the cells and HDL showed that HDL, low-density lipoprotein (LDL) or BSA at a concentration of 100 micrograms/ml in the tissue culture medium did not result in a significant difference in exogenous [3H]cholesterol efflux from the cell membrane at 37 degrees C. Proliferating T-blasts incorporated more cholesterol from HDL or LDL than did resting lymphocytes. When the cells were pulsed with 125I-HDL and chased in fresh lipid-free medium, up to 80% of the radioactivity released was not precipitable with trichloroacetic acid. This percentage decreased in a competitive manner when unlabelled HDL was present in the chase incubation medium. Finally, cultivation of lymphocytes with conditioned medium from macrophages increased Dil-HDL binding/uptake, while it was decreased by mevinolin-induced inhibition of hydroxymethylglutaryl-coA reductase. In conclusion, human lymphocytes possess a HDL binding site (receptor) responsible for lipid binding/uptake and concomitant internalization and degradation of apoproteins from HDL, but not for reverse cell membrane cholesterol transport. The activity of the binding site is up-regulated during cell proliferation and down-regulated during cell growth suppression.

High amount of epsilon-(gamma-glutamyl)lysine cross-links in Mallory bodies

Alcoholic hepatitis, the most severe form of alcoholic liver disease, is associated with inflammation, liver cell necrosis, and the appearance of Mallory bodies (MBs) in hepatocytes. Identical MBs can be experimentally induced in mouse livers by chronic griseofulvin or 3,5-diethoxycarbonyl-1,4-dihydrocollidine treatment. MBs are filamentous cytoplasmic inclusions containing insoluble high molecular weight protein material. Covalent polymerization of intracellular proteins may occur through formation of epsilon-(gamma-glutamyl)lysine cross-links catalyzed by Ca(2+)-dependent transglutaminases. Therefore, isolated experimentally-induced MBs were analyzed for the presence of epsilon-(gamma-glutamyl)lysine bonds. Highly purified MBs contained 19.7 nmole (griseofulvin-induced) and 14.4 nmoles (3,5-diethoxycarbonyl-1,4-dihydrocollidine induced) of isodipeptide linkage, respectively, per mg of protein. These results suggest that transglutaminase-induced cross-linking of proteins plays a major role in MB formation.

HIV-1 gp41 contains two sites for interaction with several proteins on the helper T-lymphoid cell line, H9

OBJECTIVE

To characterize putative binding sites for HIV-1 gp41 to H9 cells.

DESIGN

Based on accumulating evidence in the literature that HIV-1 can bind to cell surfaces independent of CD4, we attempted to clarify whether gp41, the transmembrane HIV-1 protein, contributes to CD4-independent binding. We therefore tested binding of gp41 to cells.

METHODS

Using fluorescence-activated cell-sorter analysis, we examined the binding of recombinant gp160 (gp160) and soluble gp41 (sgp41; Env amino acids 539-684) to H9 cells, and located the putative binding site(s) of gp41 by inhibition using 16 HIV-1 Env peptides. Putative HIV-1 receptor proteins in H9 cell lysates were Western blotted and precipitated using sgp41.

RESULTS

sgp41 bound to the CD4+ H9 cells and rgp160 bound to H9 cells independent of gp120-binding sites on CD4 molecules. Two gp41 peptides (Env amino acids 591-605 and 651-665) inhibited the binding of sgp41 to H9 cells. Four bands, of 37, 40, 55 and 97 kD, were blotted in H9 cell lysates, and three bands, 40, 97 and 108 kD, were observed in the precipitation analysis using lysates of 125I-surface-labelled H9 cells and sgp41 attached to sepharose beads.

CONCLUSIONS

HIV-1 gp41 contains two putative binding sites to H9 cells. These sites may be located within Env amino acids 591-605 (ERYLKDQQLLGIWGC) and 651-665 (TLLEESQNQQEKNEQ). Using two different techniques, five proteins (37, 40, 55, 97 and 108 kD) were identified in H9 lysates as possible candidates for gp41 binding.

Reversal of multidrug resistance by B859-35, a metabolite of B859-35, niguldipine, verapamil and nitrendipine

It has been shown previously that verapamil and other calcium antagonists and calmodulin inhibitors can reverse multidrug resistance. We compared the potency of the dihydropyridine derivatives (4R)-3-[3-(4,4-diphenyl-1-piperadinyl)-propyl]-5-methyl-1,4-dihydr o-2,6- dimethyl-4-(3-nitrophenyl)-pyridine-3,5-dicarboxylate-hydrochloride (B859-35), a metabolite of B859-35, niguldipine and (R)-nitrendipine to that of (RS)-verapamil in reversing multidrug resistance. The accumulation of the fluorescent dye rhodamine 123, which is transported by the P-glycoprotein, was determined by a flow cytometer. Multidrug-resistant human HeLa KB-8-5 and Walker rat carcinoma cells were incubated in the presence and in absence of the drugs indicated above. We found that 0.1 microM B859-35 increases the accumulation of rhodamine 123 in multidrug-resistant KB-8-5 and Walker cells more effectively than 1 microM (RS)-verapamil. In sensitive KB-3-1 cells addition of the drugs had no significant influence on the accumulation of rhodamine 123. IN KB-8-5 cells, 10 nM Adriamycin caused a reduction of cell growth to 85% compared to untreated controls (= 100%). If 1 microM B859-35, B859-35 metabolite, niguldipine, verapamil or (R)-nitrendipine was added to 10 nM Adriamycin, growth reduction compared with untreated controls increased to 12%, 11%, 23%, 63%, and 82% respectively. The effect of 0.1 microM B859-35 was a reduction in proliferation to 38%, that of 0.1 microM verapamil to 72%. These data illustrate that B859-35, a compound with antitumor activity in several tumors, is at least ten times more potent than racemic verapamil in reversing multidrug resistance.

Frequency of chicken CD4+ and CD8+ cells. Genetic control and effect of Rous sarcoma virus infection

In chickens from congenic inbred lines CB and CC that differ only in the major histocompatibility complex (MHC), we observed significantly different percentages of CD4+ and CD8+ cells in peripheral blood lymphocytes (PBL) and spleen. Positive cells were detected by indirect immunofluorescence test as analysed by flow cytometry. In both PBL and spleen cell suspensions, the number of CD4+ cells was significantly higher in CB than in CC chickens, whereas in CC birds there was a higher percentage of CD8+ cells than in CB. These statistically significant differences were under the MHC control. We found no statistically significant influence of regressions or progression of Rous sarcoma virus-induced tumours on the percentage of peripheral T cells and on the interleukin-2 production in vitro.

Modulation of tumour marker CA-125 expression in cultured ovarian carcinoma cells

The aim of this study was to elucidate whether proliferation of ovarian carcinoma cells may affect the biosynthesis and release of CA-125. In a cell culture model the tumour marker CA-125 expression in cytosol, surface membrane, and release into culture medium was studied in six human carcinoma cell lines. Cell cycle analysis of propidium iodide stained nuclei was performed using a fluorescent activated cell sorter. The turnover of CA-125 is very rapid, within 24 h the equivalent amount found in each cell was also released in the supernatant culture medium. A good relation between cytosolic, membrane, and released CA-125 was observed. CA-125 expression was associated predominantly with the G0/G1 phase of the cell cycle and was dependent on cell density. The results presented here demonstrate that factors associated with tumour cell proliferation could influence the CA-125 serum level in ovarian cancer patients.

Correlation of lymphocyte lipid composition membrane microviscosity and mitogen response in the aged

Healthy aged and young blood donors were investigated for the role of membrane lipid composition in the age-related increase in membrane microviscosity and decline of mitogen responsiveness. Membrane microviscosity was shown to correlate positively with membrane cholesterol/phospholipid molar ratios, which were significantly elevated in the elderly. A positive correlation also was confirmed between lymphocyte membrane microviscosity, which was measured using the probe 1,6-diphenyl 1,3,5-hexatriene, and phytohemagglutinin responsiveness of cells from the same donor. Using stepwise regression statistical analysis, the variables age, cholesterol, cholesterol/total phospholipid and phosphatidyl ethanolamine/phosphatidyl choline molar ratios were all shown to have a significant positive influence on membrane microviscosity, whereas total phospholipids had a negative effect. No statistically significant difference was seen in content of any single saturated or unsaturated fatty acid between young and old donors. After pooling, however, the proportion of all unsaturated fatty acids was significantly higher in cells from the elderly as a consequence of an increase of n-6 and n-3 polyunsaturated fatty acids. Changes in lipid composition and physical properties of lymphocyte plasma membranes may, therefore, be responsible (at least partially) for the diminution of immune reactivity in old age.

High molecular weight components are main constituents of Mallory bodies isolated with a fluorescence activated cell sorter

Mallory bodies (MBs) are cytoplasmic filamentous aggregates containing cytokeratin (CK) material. They occur in hepatocytes of patients with alcoholic liver disease (i.e., alcoholic hepatitis) and can also be induced experimentally in mice by chronic griseofulvin intoxication. To further investigate components and mechanisms involved in MB formation, a new method for MB purification was established. MBs present in a liver homogenate of griseofulvin-fed mice were labeled with a murine monoclonal antibody specific for MBs and a second fluorescein isothiocyanate-conjugated (anti-mouse IgG and IgM) antibody and subsequently isolated by two sequential sorting procedures using a fluorescence activated cell sorter (FACS). Purity of MB isolates was over 90% as revealed by computer analysis of sorting signals and fluorescence and electron microscopy. Electrophoretic separation on sodium dodecyl sulfate-polyacrylamide gels revealed three MB-related polypeptides with apparent molecular masses of 48, 55, and 65 kilodaltons but most of the highly purified MB material did not enter the gel or remained at the interphase between stacking and resolving gels. Western blotting with CK-specific antibodies showed the presence of CK epitopes in the high molecular weight MB material, which has a similar amino acid composition as normal liver CKs. These results establish that very high molecular weight material is the main constituent of MBs and suggest that a post-translational modification of CKs by covalent crosslinks is a principal mechanism of MB pathogenesis.

Glucocorticoid-regulated gene expression in the immune system. Analysis of glucocorticoid-regulated transcripts from the mouse macrophage-like cell line P388D1

To further elucidate the molecular mechanisms underlying glucocorticoid-mediated immune suppression, we have exploited cDNA cloning and subtractive screening methods to identify glucocorticoid-regulated transcripts in the mouse macrophage-like cell line, P388D1. Two of the three isolated glucocorticoid-regulated mRNA species corresponded to genes potentially important to immunoregulation: one glucocorticoid-suppressed mRNA species probably encoded the previously uncloned 3-hydroxy-3-methylglutaryl coenzyme A reductase, an enzyme that appears important for in vitro immune responses. The other mRNA species showed glucocorticoid-increased mRNA steady-state levels and was transcribed from an endogenous ecotropic type C retroviral locus. This transcript gives rise to a protein (transmembrane retroviral protein, formerly p15E), which, along with its feline and human homologs, has been implicated in immunosuppression caused by mouse, cat, and human retroviruses. Our results raise the possibility that the immunosuppressive activity of glucocorticoids might be mediated, in part, by regulating the expression of the above immunoregulatory proteins.

Glucocorticoid-regulated gene expression in the immune system. Analysis of glucocorticoid-regulated transcripts from the mouse macrophage-like cell line P388D1

To further elucidate the molecular mechanisms underlying glucocorticoid-mediated immune suppression, we have exploited cDNA cloning and subtractive screening methods to identify glucocorticoid-regulated transcripts in the mouse macrophage-like cell line, P388D1. Two of the three isolated glucocorticoid-regulated mRNA species corresponded to genes potentially important to immunoregulation: one glucocorticoid-suppressed mRNA species probably encoded the previously uncloned 3-hydroxy-3-methylglutaryl coenzyme A reductase, an enzyme that appears important for in vitro immune responses. The other mRNA species showed glucocorticoid-increased mRNA steady-state levels and was transcribed from an endogenous ecotropic type C retroviral locus. This transcript gives rise to a protein (transmembrane retroviral protein, formerly p15E), which, along with its feline and human homologs, has been implicated in immunosuppression caused by mouse, cat, and human retroviruses. Our results raise the possibility that the immunosuppressive activity of glucocorticoids might be mediated, in part, by regulating the expression of the above immunoregulatory proteins.

Increased expression of high-affinity low-density lipoprotein receptors on human T-blasts

Like all cells, lymphocytes need cholesterol for proper function, a requirement met by a finely tuned homeostasis between intracellular synthesis and uptake from the environment via low-density lipoproteins (LDL). We used flow cytometry to analyze the receptor activity of resting cells and T blasts incubated/activated in serum-free culture medium, or in medium supplemented with 25-5,000 micrograms/ml LDL. Dioctadecyl-indocarbocyanine has proved to be a useful fluorescent probe for investigating the LDL receptor activity of lymphocytes. The results show the receptor activity of day-3 resting T cells to be reduced more than 50% by 50 microgram LDL/ml, whereas 100-fold higher concentrations are necessary to achieve the same level of reduction in day-3 PHA blasts. The LDL receptor activities of individual blood donors' resting T cells, in vitro cholesterol-deprived resting T cells, and activated T blasts, were compared using two analytical techniques: spectrofluorometric analysis of detergent-solubilized cell suspensions and flow cytometric analysis of single living cells. Receptor affinity was determined by Scatchard analysis of spectrofluorometric binding curves, and by Line-weaver-Burke plots of flow cytometric data. Both methods yielded essentially identical dissociation constants (Kd) for cholesterol-deprived resting T cells and mitogen-activated T blasts, which fell in the expected range for the high-affinity LDL receptor (4.1-8.9 nM). In addition, spectrofluorometric analysis, but not flow cytometry, permitted quantification of LDL uptake.(ABSTRACT TRUNCATED AT 250 WORDS)

Tumor necrosis factor alpha maintains the viability of murine epidermal Langerhans cells in culture, but in contrast to granulocyte/macrophage colony-stimulating factor, without inducing their functional maturation

Freshly isolated murine epidermal Langerhans cells (LC) are weak stimulators of resting T cells but increase their stimulatory capacity 10-30-fold upon 2-3 d of culture together with other epidermal cells. This maturation of LC is mediated by two keratinocyte products. Granulocyte/macrophage colony-stimulating factor (GM-CSF) maintains viability and increases function. IL-1 alone does not keep LC alive, but when combined with GM-CSF further enhances their stimulatory activity. We have now searched for a cytokine that would keep LC in a viable, but functionally immature state. When LC (enriched to greater than 75%) were cultured in the presence of GM-CSF (2 ng/ml) or murine (TNF-alpha) (plateau effect at 62 U/ml), the recovery of viable LC after 72 h was identical. The LC cultured in murine TNF-alpha, however, were 10-30 times less active in stimulating resting T cells. A series of experiments demonstrated that this phenomenon was not due to the induction of insufficient amounts of GM-CSF, the induction of a suppressor factor, or a toxic effect of TNF-alpha. Interestingly, the observed TNF-alpha activity exhibited a species preference, as human TNF-alpha was not active at comparable doses. We have observed an unexpected effect of TNF-alpha on LC in vitro. Though we found that freshly prepared epidermal cells express TNF-alpha mRNA, further studies are needed to establish whether TNF-alpha plays a role in vivo by keeping resident LC in a viable, but functionally immature state.

Modulation of ovarian carcinoma tumor marker CA-125 by gamma-interferon

Interferons are known to modulate several cellular functions by the induction of different proteins. In our study a gamma-interferon-mediated presentation of one of the most important ovarian tumor markers (CA-125) on the cell surface was demonstrated using two ovarian carcinoma cell lines in vitro (HTB-77 and SKOV-3). This induction was found to be dependent on an intact protein biosynthesis. The gamma-interferon effect reached a maximum on the third day of treatment. Under such conditions the CA-125 concentration was increased intracellularly, on the cell surface, and in the supernatant culture medium. The surface antigen was shed rapidly with a half-life of 1 day. The addition of dexamethasone to gamma-interferon treated HTB-77 cells improved CA-125 expression synergistically. HLA-DR and CA-125 expression was found to be regulated by interferons in different ways. The demonstration of CA-125 expression provides an important insight into the potential regulatory mechanism governing this tumor marker. Since interferons are naturally occurring substances as well as therapeutically administered agents, it seems necessary to pay attention to possible tumor marker modulation.

An orally administered bacterial immunomodulator primes rabbit neutrophils for increased oxidative burst in response to opsonized zymosan

To assess the potential effect of an orally administered immunomodulator, consisting of a lysate of seven different bacteria, on polymorphonuclear leukocyte (PMN) function, rabbits were fed this preparation for five consecutive days via a gastric tube. On day 6, PMN were separated from peripheral blood and oxidative burst was triggered by opsonized zymosan or 12-O-tetradecanoylphorbol-13-acetate and quantitated on a single-cell basis. This study presents the extension of an existing flow cytometric method, leading to the possibility of quantitating single-cell oxidative burst triggered by particulate (instead of only soluble) stimuli. By this means, treated animals showed statistically significant increased oxidative burst reactions compared with the control group. The data provide evidence that oral application of a bacterial immunomodulator leads to a primed state in PMN for increased oxidative activity in response to a particulate stimulus. This offers the possibility that the beneficial effect of similar treatment in humans may in part be due to comparable mechanisms.

Use of a FACS III for fluorescence depolarization with DPH

We have previously demonstrated age-related differences in human lymphocyte membrane fluidity, by use of steady-state polarization measurements on bulk cell suspensions with the fluorescence probe DPH. However, for exact analysis of the possible functional importance of these changes, single-cell measurements were deemed of interest. We have now used an analog division device to measure fluorescence depolarization "p" of DPH in real time with a FACS III flow cytometer. The measurements are reliable, as we have been able to confirm the differences in DPH "p" between monocytes and lymphocytes previously shown in bulk suspension and to demonstrate the expected differences in fluidity of lipid-modulated cells. We also found significant differences in DPH "p" between lymphocytes of young and elderly blood donors. Lymphocyte subsets did not differ in polarization values but did differ in fluorescence intensity with Th less than Ts less than B = NK cells.

Promotion of lymphocyte growth by high density lipoproteins (HDL). Physiological significance of the HDL binding site

The characteristics and physiological relevance of the high density lipoprotein (HDL) binding site on unstimulated and mitogen activated human peripheral blood lymphocytes have been investigated. At 37 degrees C, specific binding/uptake of fluorescent (dioctadecylin-docarbocyanine, DiI) HDL was observed by cells from healthy donors as well as by those from low density lipoprotein receptor-defective patients; mitogen activated T-blasts exhibited a markedly elevated DiI-HDL uptake compared to resting T-cells. Binding was saturable at 37 degrees C and of high affinity, with a Kd of 5 x 10(-8) M. It was blocked by anti-apoAI polyclonal antibodies (F(ab)2 fraction), but not by anti-apolipoprotein (apo)E, anti-apoAII, or anti-apoB, and was inhibited competitively by HDL apoproteins and an apoAI-protein A fusion protein. T-cell associated DiI-HDL was increased by trypsin treatment (of the cells) and decreased by activation in the presence of HDL or low density lipoprotein. Comparison of the concentration dependencies of growth promotion and specific cell association of HDL indicated that two mechanisms of lipid exchange may be in operation: one a binding-dependent mechanism of cholesterol exchange, with maximal effect in the HDL concentration range (20-200 micrograms/ml) in which specific binding increases rapidly, and the other a binding-independent exchange of lipids effective at concentrations in which specific binding is saturated (300-5000 micrograms/ml).