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At least 145 records · Page 8Linked to original sources
PubMed1987

Polyclonal B-cell activation by a B-cell differentiation factor B151-TRF2. IV. B151-TRF2-responsive F1 B cells consist of two separate populations capable of recognizing only one of the parental I-A products expressed on B cells.

Polyclonal IgM PFC responses of unstimulated B cells induced by a B cell differentiation factor, B151-TRF2, have been shown to involve an Ia-dependent process which is inhibitable by anti-Ia monoclonal antibody (mAb). Moreover, we have demonstrated that when T cell-depleted (B10 x B10.BR)F1 (H-2b/k) spleen cells are fractionated based on their ability to bind to a B10 (H-2b) monolayer, the B151-TRF2 responses of the adherent and nonadherent cell fractions are markedly inhibited by anti-I-Ab and anti-I-Ak mAbs, respectively. From these results, we hypothesized that B cell-recognition of self-I-A products expressed on B cells is involved in the B151-TRF2-induced polyclonal B cell activation. The present study examined the genetic and cellular requirements for the successful separation of F1 B cells with parental monolayers in order to prove recognition by B cells of self-I-A products expressed on B cells. The experiments utilizing monolayers from H-2 congenic strains revealed that identity at the I-A subregion of the H-2 complex between responding F1 B cells and monolayer cells was necessary and sufficient for the successful separation of F1 B cells. In support of this conclusion, purified B cells and B cell lines expressing only parental I-A products on the surface could function effectively as monolayers. Masking of I-A determinants expressed on the monolayer with anti-I-A mAb almost completely abolished the successful separation of F1 B cells, whereas pretreatment of Ia antigens on responding F1 B cells with anti-Ia mAbs did not affect the subsequent separation, indicating involvement of receptor-I-A product interaction rather than like-like interaction in the separation of F1 B cells by the monolayer. The B151-TRF2 responses of purified B cells obtained from athymic nude mice were specifically inhibited by the relevant anti-I-A mAb but not by anti-L3T4 and anti-LFA-1 mAbs, both of which were inhibitory to the Ia-restricted T cell responses. In addition, anti-Thy1.2 mAb plus complement-treated spleen cells from athymic F1 nude mice were successfully fractionated with parental monolayer into two separate populations with restriction specificity for only one of parental I-A products. These results negate the involvement of Ia-restricted T cells in the Ia-dependent process of the B cell activation. Finally, it was demonstrated that there was no apparent difference in the expression of respective parental I-A products between F1 B cell subpopulations adherent and nonadherent to parental monolayers.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1972

Immunological memory in mice. 3. Memory to heterologous erythrocytes in both T cell and B cell populations and requirement for T cells in expression of B cell memory. Evidence using immunoglobulin allotype and mouse alloantigen theta markers with congenic mice.

Using anti-allotype sera and AKR anti thetaC3H sera, a requirement for two cell types has been demonstrated in the adoptive secondary response of mice to heterologous erythrocytes. The cell types have been designated B cells [precursors of plaque-forming cells (PFC)] and T cells (thymus-influenced cells, not providing precursors of detectable PFC). The in vivo indirect PFC response of spleen cells from primed mice is markedly reduced by in vitro treatment of the cells with a mixture of anti-theta serum and guinea pig serum (Anti theta + GPS). This B cell response is fully restored to control levels by thymus cells from normal mice which do not themselves provide precursors of indirect PFC. Thus memory is carried by the B cell lineage but the expression of this memory is dependent on the presence of a cell population which is sensitive to Anti theta + GPS and which is replaced functionally by unprimed T cells. When assayed for T cell activity, thoracic duct cells from specifically primed mice are better than cells from nonspecifically primed mice in restoring the B cell response of spleen cells from immunized mice. Moreover, the T cell activity of a reconstitutive cell population from primed mice is reduced by incubation with Anti theta + GPS. We conclude that memory to heterologous erythrocyte antigens is carried by the T cell lineage as well as the B cell lineage even though unprimed T cells are sufficient for expression of B cell memory.

Animals↗
PubMed1993

Endothelial cell Ca2+ increases upon tumor cell contact and modulates cell-cell adhesion.

The signal transduction mechanisms involved in tumor cell adhesion to endothelial cells are still largely undefined. The effect of metastatic murine melanoma cell and human prostate carcinoma cell contact on cytosolic [Ca2+] of bovine artery endothelial cells was examined in indo-1-loaded endothelial cell monolayers. A rapid increase in endothelial cell [Ca2+] occurred on contact with tumor cells, but not on contact with 8-microns inert beads. A similar increase in endothelial cell [Ca2+] was observed with human neutrophils or monocyte-like lymphoma cells, but not with endothelial cells, red blood cells, and melanoma cell-conditioned medium. The increase in endothelial cell [Ca2+] was not inhibited by extracellular Ca2+ removal. In contrast, endothelial cell pretreatment with thapsigargin, which releases endoplasmic reticulum Ca2+ into the cytosol and depletes this Ca2+ store site, abolished the cytosolic [Ca2+] rise upon melanoma cell contact. Endothelial cell pretreatment with the membrane-permeant form of the Ca2+ chelator bis-(O-aminophenoxyl)ethane-N,N,N',N'-tetraacetic acid blocked the increase in cytosolic [Ca2+]. Under static and dynamic flow conditions (0.46 dyn/cm2) bis-(O-aminophenoxyl)ethane-N,N,N',N'-tetraacetic acid pretreatment of bovine pulmonary artery endothelial cell monolayers inhibited melanoma cell adhesion to the endothelial cells. Thus, tumor cell contact with endothelial cells induces a rapid Ca2+ release from endothelial intracellular stores, which has a functional role in enhancing cell-cell adhesion.

Animals↗
PubMed2002

Apoptotic pancreatic tumor cells are superior to cell lysates in promoting cross-priming of cytotoxic T cells and activate NK and gammadelta T cells.

Tumor vaccines using dendritic cells (DCs) have been shown to induce antitumor CTL responses. The choice of the tumor antigen preparation used for DC loading is still an unresolved issue. We compared DCs pulsed with cell lysates, whole apoptotic tumor cells or their supernatants of the HLA-A2(+) human pancreatic carcinoma cell line Panc-1 for their capacity to activate T cells. Monocyte-derived DCs from HLA-A2(+) donors were pulsed with tumor antigen, matured subsequently, and cocultured with autologeous peripheral blood mononuclear cells. After three weekly restimulations with DCs, T-cell activation was assessed by intracellular IFN-gamma staining and cytotoxicity assays. Compared with lysate, pulsing DCs with the supernatant of apoptotic tumor cells induced a higher frequency of activated CTLs and T-helper cells, as well as an enhanced MHC class I-restricted tumor cell lysis. No activation of natural killer (NK) or gammadelta T cells was detected. Pulsing DCs with whole apoptotic tumor cells induced an even more pronounced lytic effect. However, in this case, MHC class-I blocking was only partially effective, and unrelated cell lines were also killed. IFN-gamma staining revealed activation of CTLs and T-helper cells, as well as NK and gammadelta T cells. Trans-well cultures of NK cells, apoptotic tumor cells, and DCs showed that NK cell activation was dependent on direct cell-to-cell contact with tumor cells and the presence of interleukin-12 produced by DCs. These results indicate that the choice of antigen preparation is a critical determinant in the induction of antitumor immunity. Tumor vaccines consisting of DCs and apoptotic tumor cells may be able to activate CTLs, as well as effector cells of the innate immune system.

Antigens, Neoplasm↗
PubMed2000

Hodgkin and Reed-Sternberg-like cells in B-cell chronic lymphocytic leukemia represent the outgrowth of single germinal-center B-cell-derived clones: potential precursors of Hodgkin and Reed-Sternberg cells in Hodgkin's disease.

In rare cases of B-cell chronic lymphocytic leukemia (B-CLL), large cells morphologically similar to or indistinguishable from Hodgkin/Reed-Sternberg (HRS) cells of Hodgkin's disease (HD) can be found in a background of otherwise typical B-CLL. To test these HRS-like cells for a potential clonal relationship to the B-CLL cells, single cells were micromanipulated from immunostained tissue sections, and rearranged immunoglobulin genes were amplified from HRS-like cells and B-CLL cells and sequenced. The same variable (V) gene rearrangements with shared and distinct somatic mutations were found in HRS-like and B-CLL cells from 1 patient, which indicates derivation of these cells from 2 distinct members of a germinal-center B-cell clone. Separate clonal V gene rearrangements were amplified from HRS-like and B-CLL cells from 2 other patients, showing concomitant presence of 2 distinct expanded B-cell clones. Epstein-Barr virus (EBV) was detected in the HRS-like cells of these 2 latter cases, indicating clonal expansion of an EBV-harboring B cell in the setting of B-CLL. There is evidence that HRS-like cells in B-CLL, like HRS cells in HD, derive from germinal-center B cells. In all cases, somatic mutations have been detected in the rearranged V genes of the HRS-like cells, and in 1 of the EBV-positive HRS-like cell clones, somatic mutations rendered an originally functional V gene rearrangement nonfunctional. We speculate that the HRS-like cells in B-CLL represent potential precursors for HRS cells causing HD.

Aged↗
PubMed2003

Cell-free DNA is released from tumor cells upon cell death: a study of tissue cultures of tumor cell lines.

To determine the source of cell-free DNA detected in the serum of cancer patients, we monitored the release of cell-free DNA and tumor markers from tumor cell lines using the cell culture technique. During the first 6 days of cell culture, we found very low concentrations of DNA and a steady increase of the CA 125 released from the SK-BR3 tumor cell lines during cell growth. A sudden increase of cell-free DNA detected in the cell medium coincided with cell death. As the cells died, the concentration of cell-free DNA declined but the concentration of CA 125 increased. The sudden release of cell-free DNA observed upon cell death was also found on the cell cultures of additional tumor cell lines, including A549, RD, and SK-N-SH cells. It appears that the majority of cell-free DNA detected in the serum of cancer patients comes from tumor cells following cell death and cell necrosis. The concentration of cell-free DNA released is related to the number of dead cells, whereas that of the tumor marker CA 125 is associated with the presence of the total number of cells (dead or alive).

Biomarkers, Tumor↗
PubMed1995

Gamma delta T cells in normal spleen assist immunized alpha beta T cells in the adoptive cell transfer of contact sensitivity. Effect of Bordetella pertussis, cyclophosphamide, and antibodies to determinants on suppressor cells.

Our prior studies showed that gamma delta T cells were required to assist alpha beta T cells in the successful adoptive cell transfer of contact sensitivity (CS) responsiveness. These TCR-gamma delta+ regulatory T cells in immune spleen and lymph node were CD3+, CD4-, CD8+, nonantigen-specific, and non-MHC-restricted. In the current work, experiments were conducted to determine the mechanisms of how the gamma delta T cells were required to assist the alpha beta T cells in CS. We found that similar regulatory gamma delta T cells were in the spleen of normal mice, but not in the spleen of nude nor SCID mice, suggesting that the regulatory gamma delta T cells were present before immunization and required the thymus for differentiation, and also required rearrangements of gamma delta V gene segments. Treatment of cell transfer recipient mice with Bordetella pertussis (Bp), or with a low dose of cyclophosphamide (50 mg/kg), restored the ability of alpha beta+ gamma delta- T cells to transfer CS. This and other results suggested that Bp caused the CS-assisting gamma delta T cells to leave the lymphoid organs (such as the spleen) and enter the circulation, and only then to be able to assist the TCR-alpha beta+ CS-effector T cells. This effect needed the simultaneous i.v. injection of the CS-effector alpha beta T cells and the CS-assisting gamma delta T cells. The results also suggested that treatment with cyclophosphamide inactivated suppressor T cells in the recipients that acted to inhibit the alpha beta T cell transfer of CS, and thus that the CS-assisting gamma delta T cells acted by protecting the CS-effector alpha beta T cells from this endogenous suppression. This suppression of CS transfers also was eliminated by treatment of recipients with two different mAbs to determinants on suppressor T cells. In conclusion, we have described regulatory TCR-gamma delta+ CS-assisting/protecting T cells that are non-antigen-specific, non-MHC-restricted, CD3+, CD8+ gamma delta T cells that may assist adoptive transferring CS-effector alpha beta T cells by making these effector T cells resistant to suppressor T cells in the normal recipients.

Animals↗
PubMed1994

Small splenic B cells that bind to antigen-specific T helper (Th) cells and face the site of cytokine production in the Th cells selectively proliferate: immunofluorescence microscopic studies of Th-B antigen-presenting cell interactions.

Antigen (Ag)-specific T helper (Th) cells regulate the proliferation and differentiation of Ag-specific B cells by secreting cytokines and by expressing activating receptors like gp39. In vitro, the cytokines and the activating receptors function in an Ag-nonspecific manner. It is unclear, therefore, how Ag specificity is imposed on B cell responses in physiological Th-B cell interactions. Here we studied, at the single cell level, the interactions between cloned Th cells and small splenic B cells, which served as Ag-specific antigen-presenting cells (APCs) to the Th cells. Digital confocal immunofluorescence microscopy of Th-B cell conjugates revealed significant variability in the molecular and cellular properties of these interactions, in spite of the fact that all the interactions in this system were expected to be Ag specific. After 30 h of incubation B cells began to divide, and this process was entirely dependent on the presence of both Th cells and Ag. Immunofluorescence microscopic studies showed that essentially all the mitotic B cells were bound to Th cells and faced the microtubule organizing center (MTOC) in the Th cells where interleukin 4 was highly concentrated. Other B cells that were bound to the same Th cells but were not close to the Th-MTOC remained in interphase. These results provide the first direct structural and functional evidence that the site of interaction of B cells with Th cells affects their immune response. We propose that, during Ag-induced Th-B cell interactions, B cells that are bound facing the Th-MTOC proliferate preferentially because they are the recipients of locally secreted cytokines. In addition, these B cells may interact with newly expressed receptors, which may also be locally inserted into the Th membrane. The polarized delivery of activating molecules towards the Th-bound APCs may impose functional specificity on effector molecules that otherwise are not Ag specific.

Animals↗
PubMed1986

Formation of mast cell colonies in methylcellulose by mouse peritoneal cells and differentiation of these cloned cells in both the skin and the gastric mucosa of W/Wv mice: evidence that a common precursor can give rise to both "connective tissue-type" and "mucosal" mast cells.

We investigated the issue of mast cell heterogeneity by cloning mast cell colonies from peritoneal cells in methylcellulose, injecting the cloned cells into the skin and stomach of mast cell-deficient (WB X C57BL/6)F1-W/Wv (WBB6F1-W/Wv) mice, and staining the mast cells that developed in these sites with Berberine sulfate, a fluorescent dye that identifies heparin-containing mast cells. When peritoneal cells of nontreated WBB6F1-+/+ mice were plated in methylcellulose containing pokeweed mitogen-stimulated spleen cell conditioned medium, pure mast cell colonies developed. In contrast, the peritoneal cavity of genetically mast cell-deficient WBB6F1-W/Wv mice lacked the progenitor cells that made mast-cell colonies. The clonal nature of the mast cell colonies was determined by using the giant granules of C57BL/6-bgJ/bgJ mice as a marker: even when mixture of peritoneal cells of C57BL/6-bgJ/bgJ mice and C57BL/6-+/+ mice were plated, all of the resulting colonies consisted of either bgJ/bgJ-type mast cells alone or +/+-type mast cells alone. Individual mast c 11 colonies of WBB6F1-+/+ mouse origin were divided into two parts; one part was directly injected into the wall of the glandular stomach of a WBB6F1-W/Wv mouse, and another part was injected into the skin of the same W/Wv mouse. Injections of 14 of 46 such colonies resulted in development of mast cells in both the "connective tissues" (skin or stomach muscle or both) and the stomach mucosa. Mast cells in the connective tissues were stained with Berberine-sulfate, indicating that they contained heparin, whereas mast cells in the stomach mucosa were not. These results suggest that a single precursor cell can give rise to both "connective tissue-type" and "mucosal" mast cells.

Animals↗
PubMed1990

Surface receptors and immune activity of purified human circulating mononuclear cells. V. Circulating null cells and a factor secreted by the null cells inhibit the synthesis of receptors for Fc mu by T cells in culture.

Receptors for Fc mu (Fc mu R) were not detected on freshly isolated unfractionated circulating human mononuclear cells (MNC) or purified T cells. However, a significant percentage of the T cells (20% to 40%), but not of the unfractionated MNC, exhibited Fc mu receptors following culture for 24 h at 37 degrees C in medium enriched with fetal calf serum. These receptors were newly synthesized by the T cells since they were not detected on T cells cultured for 24 h with cycloheximide in a non-cytotoxic concentration. The absence of Fc mu R on the cultured unfractionated MNC (of which 70% are T cells) suggested that non-T cells within the MNC-B cells and/or null cells and/or monocytes suppressed the synthesis of Fc mu R by the T cells. These cells were individually assayed for their capacity to suppress Fc mu R synthesis by co-cultured T cells. The null cells were able to totally suppress Fc mu R synthesis whereas the B cells and monocytes exhibited no suppressive activity. Null cells cultured for 24 h at 37 degrees C secreted a factor which inhibited the synthesis of receptors for Fc mu by the cultured T cells. This factor is referred to as receptor synthesis suppressor factor or RSSF. On the basis of these findings, it is concluded that (a) the circulating T cells do not possess Fc mu R; these receptors are synthesized de novo by the T cells in culture, (b) the null cells, but neither the B cells nor the monocytes, suppress the synthesis of the Fc mu R by the T cells and (c) the null cells, but neither the B cells nor the monocytes, secrete a factor, receptor synthesis suppressor factor, which can suppress the synthesis of Fc mu R by the T cells.

Cells, Cultured↗
PubMed2002

Measurements of endothelial cell-to-cell and cell-to-substrate gaps and micromechanical properties of endothelial cells during monocyte adhesion.

The interaction between monocytes and endothelial cells is considered to play a major role in the early stage of atherosclerosis, and the involved endothelial cell micromechanics may provide us with important aspects of atherogenesis. In the present study, we evaluated (i) the endothelial cell-to-cell and cell-to-substrate gaps with the electric cell-substrate impedance sensing system, which can detect the nanometer order changes of cell-to-cell and cell-to-substrate distances separately, and (ii) the endothelial cell micromechanical properties with an atomic force microscope after application of monocytes to endothelial cells. Application of monocytic THP-1 cells to IL-1beta-stimulated human umbilical vein endothelial cells immediately decreased the electrical resistance of the endothelial cell-to-substrate (increase of the cell-to-substrate gap), whereas the endothelial cell-to-cell resistance (cell-to-cell gap) did not change. The elastic modulus of the endothelial cells decreased after 2-h monocyte application, indicating an increase of endothelial cell deformability. In conclusion, the interaction of the monocytes to the endothelial cells reduced the adhesiveness to the substrate and increased the deformability of endothelial cells. These changes in the adhesiveness and the deformability may facilitate migration of monocytes, a key process of atherogenesis in the later stage.

Actins↗
PubMed1995

An analysis of the growth of the retinal cell population in embryonic chicks yielding proliferative ratios, numbers of proliferative and non-proliferative cells and cell-cycle times for successive generations of cell cycles.

Growth curves of the retinal cell population of embryonic chicks were fitted by a branching-process model of cell population growth, thereby estimating the proliferative ratios and mean cell-cycle times of the generations of cell cycles that underlie retinal growth. The proliferative ratio determines the proportion of cells that divides in the next generation, so the numbers of proliferative and non-proliferative cells in each generation of cell cycles were obtained. The mean cell-cycle times determine the times over which the generations are extant. Assuming growth starts from one cell in generation 0, the proliferative cells reach 3.6 x 10(6) and the non-proliferative cells reach 1.1 x 10(6) by generation 23. The next four generations increase the proliferative cell numbers to 13.9 x 10(6) and produce 20.1 x 10(6) non-proliferative cells. In the next five generations in the end phase of growth, non-proliferative cells are produced in large numbers at an average of 13.9 x 10(6) cells per generation as the retinal lineages are completed. The retinal cell population reaches a maximum estimated here at 98.2 x 10(6) cells. The mean cell-cycle time estimates range between 6.8 and 10.1 h in generations before the end phase of growth and between 10.6 and 17.2 h in generations in the end phase. The retinal cell population growth is limited by the depletion of the proliferative cell population that the production of non-proliferative cells entails. The proliferative ratios and the cell-cycle-time distribution parameters are the likely determinants of retinal growth rates. The results are discussed in relation to other results of spatial and temporal patterns of the cessation of cell cycling in the embryonic chick retina.

Animals↗
PubMed2006

Hybrid cells formed by fusion of Epstein-Barr virus-associated B-lymphoblastoid cells and either marrow-derived or solid tumour-derived cell lines display different co-stimulatory phenotypes and abilities to activate allogeneic T-cell responses in vitro.

A panel of stable cell hybrids was generated by fusing a range of marrow-derived and solid tumour-derived human cell lines with the B-lymphoblastoid cell lines, HMy2 or KR4, and expression of immunologically relevant accessory and co-stimulatory molecules, and ability to stimulate allogeneic T-cell responses in vitro was investigated. Hybrid cell lines generated from three marrow-derived tumour cells consistently expressed both MHC class I and class II molecules, a range of accessory and T-cell co-stimulatory ligand molecules, including CD80 and CD86, and directly stimulated markedly enhanced T-cell proliferative responses in vitro, as compared with the parent tumour cell lines. The responses were blocked by addition of CTLA4-Ig fusion protein to the cultures, indicating a role of CD28/B7 interaction in induction of T-cell activation. By contrast, hybrid cells derived from three solid tumours only expressed MHC class II when the parent tumour cell line expressed MHC class II and consistently failed to express CD80 or CD86. These hybrid cells also stimulated greater T-cell proliferative responses in vitro than the parent tumour cell lines, although effective co-stimulation depended on the presence of responder non-T cells in the cultures. The expression of co-stimulatory ligand molecules and ability to directly stimulate strong allogeneic T-cell responses correlated with the EBV latency type of the hybrid cells. These data suggest that phenotypic and functional differences in fusion cells of professional antigen- presenting cells and tumour cells arise as a result of the parent tumour cell type.

Antigen-Presenting Cells↗
PubMed1988

Defective helper function of purified T4 cells and excessive suppressor activity of purified T8 cells in patients with B-cell chronic lymphocytic leukemia. T4 suppressor effector cells are present in certain patients.

We investigated helper and suppressor functions to B-cell responses and T-T cell interactions of purified T4 and T8 cells from 20 untreated patients with B-cell chronic lymphocytic leukemia (CLL). Appropriate mixtures of purified T4 or T8 cells from patients with CLL were cultured with purified B cells or T4 and B cells from normal donors for 7 days with pokeweed mitogen (PWM). IgM, IgA, and IgG produced were determined in the supernatants of these cultures by a heavy chain-specific enzyme-linked immunosorbent assay (ELISA) and compared to those obtained by the corresponding mixtures of T4, T8, and B cells from normal donors. Purified T4 cells from 14 of 20 patients with CLL exhibited defective helper function (P less than .001) to immunoglobulin (Ig) production by purified B cells from normal donors. Purified T4 cells from 6 of these 14 patients were able to suppress significantly (P less than .001) and in a concentration-dependent manner Ig production by mixtures of T4 and B cells from normal donors, in the absence of T8 cells. These suppressor effector T4 cells from certain patients were partially radiosensitive. Purified T8 cells from 8 of 20 patients with CLL exhibited excessive suppressor activity. These cells significantly suppressed (P less than .001), Ig production by mixtures of T4 and B cells from normal donors to a degree significantly higher (P less than .005) than that observed by equal numbers of T8 cells from normal donors. This inhibition was dependent on the numbers of the T8 CLL cells added to the cultures. Excessive suppressor activity by T8 CLL cells was at least in part radiosensitive in four of eight patients. These results demonstrate a wide range of immunoregulatory T-cell abnormalities in patients with CLL. Naturally occurring T4 suppressor effector cells, directly inhibiting Ig production by mixtures of T4 and B cells, in the absence of T8 cells, are present in certain patients with CLL.

Antibody Formation↗
PubMed2006

Transmission in vitro of hepatitis C virus from persistently infected human B-cells to hepatoma cells by cell-to-cell contact.

Virus cell-to-cell spread has been reported for many different viruses and may contribute to pathogenesis of viral disease. The role played by cell-to-cell contact in hepatitis C virus (HCV) transmission was studied in vitro by cell co-cultivation experiments. A human lymphoblastoid B-cell line, infected persistently with HCV in vitro (TO.FE(HCV)), was used as HCV donor [Serafino et al., 2003]; recipient cells were the human hepatoma HepG2 cell line. Both cell types were co-cultured for 48 hr to allow the cell-to-cell contacts. The hepatoma HepG2 cells are not permissive to free-virus infection, but they were infected successfully using TO.FE(HCV) cells as source of virus. The kinetics of viral RNA synthesis and the percentage of infected cells were compared in cell-mediated-and cell-free-viral infection. After co-cultivation, a consistent proportion of hepatoma cells replicated HCV and stably expressed viral antigens. Virus produced was infectious as demonstrated by the ability to reinfect fresh B-cells. This cell model shows that permissiveness to HCV infection can be achieved in vitro in non-permissive hepatoma cells by direct cell-to-cell contacts with infected human B-cells. This mechanism of virus spread may also play a pathogenic role in vivo.

B-Lymphocytes↗
PubMed1991

Natural killer (NK) cell response to virus infections in mice with severe combined immunodeficiency. The stimulation of NK cells and the NK cell-dependent control of virus infections occur independently of T and B cell function.

The activation, proliferation, and antiviral properties of natural killer (NK) cells were examined in severe combined immunodeficiency (SCID) mice to determine the influence of mature T or B cells on virus-induced NK cell functions and to more conclusively determine the antiviral properties of prototypical CD3- NK cells. NK cells were activated to high levels of cytotoxicity 3 d after infection of mice with lymphocytic choriomeningitis virus (LCMV) or murine cytomegalovirus (MCMV). Analyses of spleen leukocytes from LCMV-infected mice by a variety of techniques indicated that the NK cells proliferated and increased in number during infection. Propidium iodide staining of the DNA of cycling cells revealed that the great majority of proliferating spleen leukocytes 3 d after LCMV infection was of the NK cell phenotype (CD3-, Ig-, Mac-1+, CZ1+, 50% Thy-1+), in contrast to uninfected mice, whose proliferating cells were predominantly of other lineages. Analyses of the NK cell responses over a 2 wk period in control CB17 mice infected with MCMV indicated a sharp rise in serum interferon (IFN) and spleen NK cell activity early (days 3-5) in infection, followed by sharp declines at later stages. In SCID mice the IFN levels continued to rise over a 10-d period, whereas the NK cell response peaked on day 3-5 and gradually tapered. In contrast to the immunocompetent CB17 mice, SCID mice did not clear the MCMV infection and eventually succumbed. SCID mice, again in contrast to immunocompetent CB17 mice, also failed to clear infections with LCMV and Pichinde virus (PV); these mice, infected as adults, did not die but instead developed long-term persistent infections. Depletion of the NK cells in vivo with antiserum to asialo GM1 rendered both SCID and CB17 control mice much more sensitive to MCMV infection, as shown by titers of virus in organs and by survival curves. In contrast, similar depletions of NK cells did not enhance the titers of the NK cell-resistant virus, LCMV. Two variants of PV, one sensitive to NK cells and the other selected for resistance to NK cells by in vivo passage, were also tested in NK cell-depleted SCID mice. The NK-sensitive PV replicated to higher titers in NK cell-depleted SCID mice, whereas the titers of the NK cell-resistant PV were the same, whether or not the mice had NK cells. These experiments support the concept that CD3- prototypical NK cells mediate resistance to NK cell-sensitive viruses via a mechanism independent of antiviral or "natural" antibody.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗