Biomedical subjects

M Wysocka

Publications and source records attributed to M Wysocka.

At least 55 records · Page 3Linked to original sources

PubMed1995

Dendritic cells produce IL-12 and direct the development of Th1 cells from naive CD4+ T cells.

Dendritic cells are APCs that are unique in their potency to stimulate proliferation of primary Ag-specific responses in vitro and in vivo. In this study, we demonstrate that dendritic cells can produce IL-12, a dominant cytokine involved in the development of IFN-gamma-producing T cells. This finding resulted from our observations that dendritic cell-induced Th1 development from total CD4+ T cells upon neutralization of endogenous levels of IL-4 was IL-12-dependent. Furthermore, we demonstrate that dendritic cells can induce the development of Th1 cells from Ag-specific naive LECAM-1bright CD4+ T cells obtained from alpha beta-TCR transgenic mice, provided that CD4+ LECAM-1dull T cells, which produce significant levels of IL-4, are not present in the primary cultures. Production of IL-12 by dendritic cells was confirmed by positive immunofluoresence staining with Abs specific for the inducible IL-12 p40 subunit. This suggests that in addition to inducing proliferation and clonal expansion of naive T cells, dendritic cells, by their production of IL-12, play a direct role in the development of IFN-gamma-producing cells that are important for cell-mediated immune responses.

Animals↗

PubMed1995

IL-12 is required for natural killer cell activation and subsequent T helper 1 cell development in experimental leishmaniasis.

Infection of mice with the protozoan Leishmania major is an established in vivo model for the definition of factors that contribute to CD4+ T helper cell subset development. In the current study, a central role for IL-12 in directing both the innate and adaptive immune responses to L. major is established. We show that in vivo neutralization of IL-12 eliminates the NK cell cytotoxic response and IFN-gamma production by lymph node cells from 2-day L. major-infected C3H mice. Moreover, anti-IL-12 treatment abrogated Th1 cell development and enhanced Th2 cell development. Consistent with these results, elevated IL-12 p40 production and an increase in the number of IL-12 p40-producing cells were observed within 1 day of infection in C3H mice. Because BALB/c mice lack an early NK cell response or a Th1-type immune response after L. major infection, we investigated the possibility that they had a defect in the ability to produce IL-12. Surprisingly, L. major infection stimulated IL-12 p40 production in BALB/c mice early after infection. Further studies suggest that BALB/c mice are unable to generate an early IFN-gamma response because of the simultaneous production of IL-12 and cytokines that inhibit IL-12 function, such as TGF-beta, IL-4, and IL-10. Together, these data show that IL-12 regulates the immune response to L. major, but that even when IL-12 is induced, Th1 cell development may be interrupted by simultaneous production of inhibitory cytokines.

Animals↗

PubMed1995

CD4 T cells inhibit in vivo the CD8-mediated immune response against murine colon carcinoma cells transduced with interleukin-12 genes.

Retroviral-mediated cytokine gene transfer into tumor cells is a highly effective way of inducing tumor inhibition and immunity. We analyzed the tumorigenicity of C-26 murine colon carcinoma cells transduced with genes encoding the two subunits of murine interleukin-12 (IL-12) in a polycistronic retroviral vector and selected for resistance to G418 and for IL-12 production (30-80 pg/ml). BALB/c mice injected s.c., i.v. and intrasplenically with C-26/IL-12 cells from three different IL-12-producing clones showed delayed tumor onset as compared with mice injected with control NeoR-transduced or parental tumor cells. Although C-26/IL-12 tumor-bearing mice eventually died of lung metastasis, their survival time was twice as long as that of mice injected with control cells. In experiments with mice selectively depleted of natural killer (NK) cells before tumor cell injection, the time of tumor onset and survival of mice injected with C-26/IL-12 s.c. and i.v., respectively, was reduced. CD8+ T cell depletion had no effect on latency or survival, whereas removal of CD4+ T cells led to C-26/IL-12 tumor regression in about 40% of mice. Histological and immunocytochemical characterization of leukocytes infiltrating C-26/IL-12 tumors showed only slight infiltration with few T cells in non-depleted mice but abundant infiltration by CD8+ T cells and asialo-GM1+ NK cells in tumors of mice depleted of CD4+ T cells. The lack of CD8+ T cell infiltration is not due to a CD4-mediated suppression of their activation because irradiated C-26/IL-12 cells primed for the induction of a strong cytotoxic T lymphocyte response against C-26 parental cells and induced CD8+ effector cells that protected against C-26/IL-12 in a Winn assay. Rather, the results suggest that, although C-26/IL-12 cells injected in vivo stimulate both NK and CD8+ T cells, tumor infiltration by the latter is inhibited by CD4+ T cells.

Animals↗

PubMed1995

Interleukin-12 is required for interferon-gamma production and lethality in lipopolysaccharide-induced shock in mice.

Several cytokines, in particular tumor necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma), have been shown to be responsible for pathological reactions which may lead to shock and death observed in infection with Gram-negative bacteria and in response to endotoxins (lipopolysaccharides, LPS). Priming of mice with the avirulent Bacille Calmette Guérin (BCG) vaccine strain of Mycobacterium bovis increases the sensitivity of mice to the lethal effect of LPS and results in an efficient priming for cytokine production. In response to low doses (1 microgram/mouse) of LPS, BCG-primed mice produce interleukin-12 (IL-12) which controls IFN-gamma production, as demonstrated by the ability of neutralizing anti-IL-12 antibodies to suppress IFN-gamma production. However, the concentration of the biologically active IL-12 p70 heterodimer is similar in the serum of both BCG-primed or unprimed mice, reaching levels of 1-3 ng/ml at 3-6 h after LPS injection, whereas IFN-gamma production was observed only in BCG-primed mice. The priming effect of BCG on IFN-gamma production appears to be mostly due to its ability to increase TNF-alpha production, which acts as cofactor with LPS-induced IL-12 in inducing IFN-gamma production, as shown by the ability of injection of TNF-alpha and LPS (1 microgram/mouse), but not LPS alone, to induce IFN-gamma production. However, in addition to TNF-alpha, other LPS-induced cofactor(s) are required in cooperation with IL-12 to induce optimal IFN-gamma production, because co-injection of TNF-alpha and IL-12, sufficient to induce serum concentrations of both cytokines higher and more persistent than those obtained by injection of LPS, was not sufficient to induce IFN-gamma production in vivo. Neutralizing anti-IL-12 antibodies, in addition to inhibiting the in vivo LPS-induced IFN-gamma production, also completely protect BCG-primed mice injected with up to 10 micrograms of LPS from shock-induced death. Thus, IL-12 is required for IFN-gamma production and lethality in an endotoxic shock model in mice.

Animals↗

PubMed1994

Parasite-induced IL-12 stimulates early IFN-gamma synthesis and resistance during acute infection with Toxoplasma gondii.

In vitro and in vivo studies were performed to assess the involvement of IL-12 in resistance to acute and chronic infection with an avirulent strain of Toxoplasma gondii. Our previous findings implicated macrophages as a major source of parasite-induced IL-12. This finding was confirmed by showing that peritoneal macrophages exposed to either live parasites or soluble tachyzoite Ags produce IL-12 protein. In mice, increased expression of IL-12 (p40) mRNA in both spleen and peritoneal cells was detected as early as 2 days postinfection. Treatment with neutralizing mAbs against IL-12 increased the susceptibility of C57BL/6, BALB/c, and severe combined immunodeficient (SCID) mice to acute infection, which resulted in 100% mortality within the first 15 days after parasite inoculation. In contrast, neutralization of endogenously produced IL-12 had no effect when given during chronic infection. In agreement with the survival data, treatment with anti-IL-12 resulted in decreased IFN-gamma and enhanced Th2 (IL-4 and IL-10) cytokine synthesis by splenocytes when given during acute, but not chronic, toxoplasmosis. Sorting experiments on spleen cells from acutely infected mice indicated that both CD4+ lymphocytes and NK1.1+/CD3- cells contribute to the early IFN-gamma response. In contrast, CD4+ cells were found to be the major source of the cytokine during chronic disease. Together, these results suggest that the stimulation of macrophage-derived IL-12 plays a major role in both the induction of resistance and Th1 cell subset selection in acute T. gondii infection, but may not be required to maintain established immunity.

Animals↗

PubMed1994

Interleukin 12, interferon gamma, and tumor necrosis factor alpha are the key cytokines of the generalized Shwartzman reaction.

The Shwartzman reaction is elicited by two injections of lipopolysaccharide (LPS) in mice. The priming LPS injection is given in the footpad, whereas the lethal LPS challenge is given intravenously 24 h later. The injection of interferon gamma (IFN-gamma) or interleukin 12 (IL-12) instead of the LPS priming injection induced the lethal reaction in mice further challenged with LPS. Antibodies against IFN-gamma when given together with the priming agent, prevented the lethal reaction in mice primed with either LPS, IL-12, or IFN-gamma. Antibodies against IL-12, when given together with the priming agent, prevented the lethal reaction in mice primed with either LPS or IL-12 but not with IFN-gamma. These results strongly suggest that LPS induces the release of IL-12, that IL-12 induces the production of IFN-gamma, and that IFN-gamma is the cytokine that primes macrophages and other cell types. Upon LPS challenge, the lethal Shwartzman reaction is induced by a massive production of inflammatory cytokines that act on the target sites already sensitized by IFN-gamma. If mixtures of TNF and IL-1 or mixtures of TNF and IFN-gamma are used to challenge mice previously primed with IFN-gamma or IL-12, mortality is induced. In the same conditions, the individual cytokines or a mixture of IL-1 and IFN-gamma do not replace the LPS challenge. When the mice are primed with LPS, the combination of TNF, IL-1, and IFN-gamma induced only a partial mortality incidence suggesting that the involvement of other LPS-induced factors.

Animals↗

PubMed1994

B7 and interleukin 12 cooperate for proliferation and interferon gamma production by mouse T helper clones that are unresponsive to B7 costimulation.

We have previously shown that dendritic cells isolated after overnight culture, which can express B7 and are potent stimulators of naive T cell proliferation, are relatively poor at inducing the proliferation of a panel of murine T helper 1 (Th1) clones. Maximal stimulation of Th1 clones was achieved using unseparated splenic antigen presenting cells (APC). An explanation for these findings is provided in the present study where we show that FcR+ L cells transfected with B7 stimulate minimal proliferation of Th1 clones in response to anti-CD3 antibodies, in contrast to induction of significant proliferation of naive T cells. However, addition of interleukin 12 (IL-12) to cultures of Th1 cells stimulated with anti-CD3 and FcR+ B7 transfectants resulted in a very pronounced increase in proliferation and interferon gamma (IFN-gamma) production. Exogenous IL-12 did not affect the B7-induced proliferation of naive T cells. This showed that whereas costimulatory signals delivered via B7-CD28 interaction are sufficient to induce significant proliferation of naive T cells activated through occupancy of the T cell receptor, Th1 T cell clones require cooperative costimulation by B7 and IL-12. This costimulation was shown to be specific by inhibition of proliferation and IFN-gamma production using chimeric soluble cytolytic T lymphocyte-associated antigen 4-human IgG1Fc (CTLA4-Ig) and anti-IL-12 antibodies. Furthermore, the significant antigen specific proliferation and IFN-gamma production by Th1 clones observed when splenocytes were used as APC was almost completely abrogated using CTLA4-Ig and anti-IL-12 antibodies. Thus two costimulatory signals, B7 and IL-12, account for the ability of splenic APC to induce maximal stimulation of Th1 clones. IL-10 downregulates the expression of IL-12 by IFN-gamma-stimulated macrophages and this may account largely for t the ability of IL-10 to inhibit APC function of splenic and macrophage APC for the induction of Th1 cell proliferation and IFN-gamma production. Indeed we show that IL-12 can overcome the inhibitory effect of IL-10 for the APC-dependent induction of proliferation and IFN-gamma production by Th1 clones. These results suggest that proliferation by terminally differentiated Th1 clones, in contrast to naive T cells, requires stimulation via membrane-bound B7 and a cytokine, IL-12. It is possible that these signals may result in the activation of unresponsive T cells during an inflammatory response. IL-10, by its role in regulating such innate inflammatory responses, may thus help to maintain these T cells in an unresponsive state.

Abatacept↗

PubMed1994

Identification of overlapping class I and class II H-2d-restricted T cell determinants of influenza virus N1 neuraminidase that require infectious virus for presentation.

The requirement for endogenous viral protein synthesis in helper and cytotoxic T cell (CTL) recognition of influenza virus was studied at the level of individual epitopes. The viral envelope glycoprotein neuraminidase (NA) contains class I and class II major histocompatibility complex (MHC)-restricted T cell determinants that are presented by virus-infected antigen-presenting cells (APC). We had previously shown that recognition of NA by class II I-Ed-restricted T cells required either active viral infection of APC or introduction of uv-inactivated virus to the cytosol, similar to the well-established requirements for class I-restricted responses. Detailed mapping of T cell epitopes was undertaken using vaccinia virus vectors encoding truncated segments of the influenza NA molecule and by synthetic peptides. Class I MHC-restricted CTL were found to recognize two regions of NA: residues 69-89 in the context of Dd and 191-201 presented by Kd. Analyses of T cell proliferation and T hybridoma clones revealed that class II-restricted responses recognized the same two regions as the CTL, presented by I-Ed and I-Ad, respectively. Interestingly, both class I and class II MHC-restricted T cells showed similar requirements for endogenously synthesized antigen, responding poorly or not at all to endocytosed uv-inactivated virus. This extends previous observations that specific epitopes can be preferentially presented by class II molecules from endogenously synthesized antigens and shows that the same antigenic determinants can have access to both class I and class II antigen presentation pathways.

Amino Acid Sequence↗

PubMed1994

The adjuvant effect of interleukin-12 in a vaccine against Leishmania major.

Protection induced by vaccination depends on the capacity of the vaccine to elicit an appropriate immune response. In leishmaniasis, protection requires leishmanial-specific CD4+ T helper (TH) cells. Vaccination of BALB/c mice with leishmanial antigens and interleukin-12 (IL-12) promoted the development of leishmanial-specific CD4+ TH1 cells. These mice were resistant to subsequent infection with Leishmania major. Thus, IL-12 is an effective adjuvant for the initiation of protective cell-mediated immunity against leishmaniasis and may be an important component in other vaccines that need to induce cell-mediated immunity.

Adjuvants, Immunologic↗

PubMed1994

B lymphocyte and macrophage expression of carcinoembryonic antigen-related adhesion molecules that serve as receptors for murine coronavirus.

The expression of carcinoembryonic antigen (CEA)-related glycoproteins that have been associated with intercellular adhesion and that serve as receptors for mouse hepatitis virus (MHV) was analyzed in cells from the immune system of BALB/c mice using immunolabeling and RNA polymerase chain reaction amplification of receptor transcripts. These glycoproteins, which are called biliary glycoproteins, were highly expressed in B lymphocytes, including cells of the B-1a (CD5+) lineage, and in macrophages, but were not detectable in resting T lymphocytes. Similarly, murine cell lines of B cell and macrophage origin expressed messenger RNA encoding CEA-related molecules, while the corresponding mRNA was only slightly detectable in a T cell line. These CEA-related cell adhesion glycoproteins were also expressed in endothelial cells. Therefore, their specific interaction with their so far unknown ligand may be of functional importance in cellular interactions in the immune response. Monoclonal antibody directed against these glycoproteins blocked MHV-A59 infection of the B cell-derived SP20 cell line. Thus, the functional receptors for MHV on B lymphocytes, like those on murine fibroblasts, are isoforms of CEA-related glycoproteins. Treatment of B cells with anti-receptor antibody also blocked B cell-mediated cytotoxicity against MHV-A59-infected fibroblasts, indicating that this phenomenon is mediated by interaction of viral attachment protein on the infected target cells with specific CEA-related receptor glycoproteins on the effector B cells.

Animals↗

PubMed1994

Infection with Leishmania major induces interleukin-12 production in vivo.

Experimental infections of mice with the protozoan parasite Leishmania major provide an excellent model for defining the conditions required for generation of CD4+ Th1 and Th2 cells in vivo. Since interleukin-12 (IL-12) has been implicated in the development of Th1 cells, we investigated whether L. major stimulates IL-12 production in vitro or in vivo. Surprisingly, macrophages cultured in vitro failed to produce IL-12 following L. major infection. In contrast, lymph node cells from C3H mice infected for 2 days with L. major produced elevated levels of IL-12. In order to determine if the inability to stimulate IL-12 production was limited to in vitro infections, we infected macrophages in vivo by inoculating L. major into the peritoneal cavity. Peritoneal cells isolated 24 h later exhibited a significant increase in the number of cells producing IL-12. In addition, supernatants harvested from these cells following culture contained elevated levels of IL-12. These data indicate that L. major infection induces increased IL-12 production in mice.

Animals↗

PubMed1992

Natural killer cell stimulatory factor (NKSF) or interleukin-12 is a key regulator of immune response and inflammation.

Natural Killer cell Stimulatory Factor (NKSF) or interleukin-12 (IL-12) is a heterodimeric cytokine of 70 kDa formed by a heavy chain of 40 kDa (p40) and a light chain of 35 kDa (p35). Although it was originally identified and purified from the supernatant of Epstein-Barr virus-transformed B cell lines, it has been shown that among peripheral blood cells NKSF/IL-12 is predominantly produced by monocytes, with lower production by B cells and other accessory cells. The most powerful inducers of NKSF/IL-12 production are bacteria, bacterial products and parasites. In addition to the biologically active p70 heterodimer, the cells producing NKSF/IL-12 also secrete a large excess of monomeric p40, a molecule with no demonstrable biological activity. NKSF/IL-12 is active on T lymphocytes and NK cells on which it induces production of lymphokines, enhancement of cytotoxic activity and mitogenic effects. NKSF/IL-12 induces T and NK cells to produce IFN-gamma and synergizes with other IFN-gamma inducers in this effect. In vitro, and probably in vivo, NKSF/IL-12 is required for optimal IFN-gamma production. When human lymphocytes are stimulated with antigens in vitro, addition of exogenous NKSF/IL-12 to the culture induces differentiation of T helper type 1 (Th1) cells, whereas neutralization of endogenous NKSF/IL-12 with antibodies favors differentiation of Th2 cells. IFN-gamma, a product of Th1 cells, enhances NKSF/IL-12 production by mononuclear cells, whereas IL-10 and IL-4, products of Th2 cells, efficiently inhibit it. Therefore, NKSF/IL-12 appears to be an important inducer of Th1 responses produced by accessory cells during early antigenic stimulation and its production is regulated by a positive feedback mechanism mediated by Th1 cells through IFN-gamma and a negative one by Th2 cells through IL-10 and IL-4. The balance of IL-12 production versus IL-10 and IL-4 production early during an immune response might therefore be instrumental in determining Th1-type versus Th2-type immune responses. Because of this potential role of IL-12 during immune responses, our results demonstrating the impaired ability of HIV seropositive patients to produce NKSF/IL-12 in response to bacterial stimulation suggest that this defect in NKSF/IL-12 production might be a factor contributing to their immune depression.

Acquired Immunodeficiency Syndrome↗

PubMed1992

Influenza virus infection elicits class II major histocompatibility complex-restricted T cells specific for an epitope identified in the NS1 non-structural protein.

A T cell epitope of the influenza virus NS1 molecule was identified and shown to be a determinant used in class II major histocompatibility complex-restricted T cell responses to infectious virus. An I-Ed-restricted BALB/c mouse T hybridoma clone recognizing influenza virus A/Puerto Rico/8/34 (PR8; subtype H1N1) but not A/Udorn/72 (subtype H3N2) secreted lymphokines in response to purified recombinant NS1 or fusion proteins containing amino acids 1 to 81 or 1 to 42 of NS1. As expected for recognition of a non-virion protein, the clone failed to respond to u.v.-inactivated virus. The antigenic determinant was localized by synthetic peptides to amino acids 13 to 32 of NS1, explaining the lack of recognition of A/Udorn/72 virus which has an alanine to valine substitution at position 23 within the determinant. A single intranasal dose of infectious PR8 virus was found to elicit T cells that responded to peptide NS1 13-32, suggesting that this determinant is a significant target of T cells in normal infections. To stimulate helper T cell responses similar to those achieved with infectious virus, influenza virus vaccines may therefore have to include NS1 in addition to virion components.

Amino Acid Sequence↗

PubMed1992

Herpes simplex virus type 1 mutant strain in1814 establishes a unique, slowly progressing infection in SCID mice.

Ocular infection of immunocompetent (BALB/c) mice with wild-type herpes simplex virus type 1 (HSV-1) 17+ may lead to acute fatal encephalitis; however, in surviving animals, a latent (nonproductive) infection of the nervous system is established. In contrast, 17+ infection invariably kills mice with severe combined immunodeficiency (SCID mice) within 2 weeks. Ocular infection of immunocompetent mice with a mutant HSV-1 strain, in1814, which does not produce a functional alpha-transinducing protein, results in no detectable viral replication in the nervous system during the time corresponding to the acute phase of infection, no mortality, and the establishment of latency. In SCID mice, however, the in1814 virus establishes a unique, slowly progressing infection. In studying the courses of in1814 infection in SCID and BALB/c mice, we found that although intact B- and/or T-lymphocytic functions were required for the control of viral replication in the nervous system, some of the infected neurons of SCID mice seemed to be able to restrict in1814 replication and harbor the virus in a latent state.

Animals↗

PubMed1991

Class II MHC-restricted T cell determinants processed from either endosomes or the cytosol show similar requirements for host protein transport but different kinetics of presentation.

We have studied the role of APC protein transport in presentation of class II MHC-restricted T cell determinants of influenza virus glycoproteins that have distinct Ag processing requirements. Two I-Ed-restricted epitopes were analyzed: hemagglutinin (HA) 111-119, which is processed by the exogenous/endocytic pathway, and neuraminidase (NA) 79-93, which has a requirement for cytosolic processing. NA 79-93 is presented from infectious but not non-replicative virus under ordinary conditions. This requirement for viral biosynthesis could be bypassed by using a soluble inhibitor of NA,2,3-dehydro-2-deoxy-N-acetyl neuraminic acid (DDAN), to facilitate cytosolic introduction of virus. APC exposed to UV virus/DDAN present HA and NA determinants derived directly from proteins of the input virus particles. This allows presentation of both endocytically and cytosolically processed epitopes in the same experiment using noninfectious virus. The inhibitor brefeldin A (BFA) was used to interrupt host protein transport at various times relative to virus/DDAN addition. We observed that BFA added simultaneously with virus blocked recognition of NA 79-93 but not HA 111-119. This distinction was found to be based upon different expression kinetics of the HA and NA determinants. Expression of NA 79-93 required 6 to 9 h, whereas HA 111-119 was presented by 1 h after Ag addition. When APC were incubated with BFA at intervals before virus addition, presentation of HA 111-119 was also blocked as a function of time. Data indicate that about 5 h of BFA treatment is needed to deplete host protein pools required for presentation of I-Ed-restricted T cell determinants processed from either endosomes or the cytosol.

Animals↗

PubMed1991

Immunogenic peptides of influenza virus subtype N1 neuraminidase identify a T-cell determinant used in class II major histocompatibility complex-restricted responses to infectious virus.

Six nonoverlapping peptides of the neuraminidase (NA) glycoprotein of influenza virus A/Puerto Rico/8/34 (H1N1) (PR8 virus) were found to be immunogenic for proliferating T cells when injected into BALB/c mice in Freund adjuvant. T cells elicited by peptide immunization could recognize PR8 virus in vitro. However, only one of these peptides, corresponding to residues 79 to 93 of NA (NA 79-93), was able to restimulate T cells of mice immunized with infectious virus. T cells that recognized this peptide were uniformly I-Ed restricted, yet infectious influenza virus was required for responses. NA 79-93-specific T-hybridoma clones raised by immunization either with whole virus or with the synthetic peptide alone each responded to replicative virus and not to UV-inactivated virions. These data suggest that the NA 79-93 T-cell determinant which is commonly presented during an encounter with influenza virus in vivo is processed preferentially from NA synthesized within antigen-presenting cells.

Amino Acid Sequence↗

PubMed1990

Class I H-2d-restricted cytotoxic T lymphocytes recognize the neuraminidase glycoprotein of influenza virus subtype N1.

Class I major histocompatibility complex-restricted cytotoxic T lymphocytes (CTL) that recognize the neuraminidase (NA) glycoprotein of subtype N1 influenza A viruses have been demonstrated in BALB/c mice. Responses to NA were obtained only in protocols that use two in vivo inoculations of virus, including a recombinant vaccinia virus containing the NA of subtype N1 influenza virus (NA-VAC) to prime or boost. Restimulation in vitro was also required for CTL recognition of NA and strongly depended on the specific N1 virus used. Influenza viruses A/Puerto Rico/8/34 (H1N1), A/CAM/46 (H1N1), J1 (H3N1), and JAP/BEL (H2N1), but not A/Bellamy (H1N1) or MEM/BEL (H3N1) virus, were able to stimulate NA-specific memory T cells in vitro. Single or double in vivo inoculation of any of the N1 viruses or a single injection of NA-VAC failed to elicit restimulatable NA-specific CTL. Lysis of NA-VAC-infected cells at low effector/target ratios was comparable to that observed toward other influenza virus proteins known to be major targets of CTL in BALB/c mice, indicating that antigenic determinants of the subtype N1 NA molecule can be efficiently presented in the context of major histocompatibility complex class I.

Animals↗

PubMed1989

Target and effector cell fusion accounts for B lymphocyte-mediated lysis of mouse hepatitis virus-infected cells.

In confirmation of previous reports, we observed lysis of mouse hepatitis virus (MHV)-infected target cells in the presence of spleen and lymph node cells from nonimmunized mice possessing a B cell surface phenotype (IgM+, IgG+, J11d+, Ia+, Fc+, Thy1-, MAC-1- and asialo-GM1-). Lysis was inhibited by MHV-specific antisera. The presence of immunoglobulin at the surface of B cells is not required for cytolysis since MHV-infected target cells are lysed in the presence of the B cell hybridoma Sp2/0, which fails to synthesize immunoglobulin. Using 51Cr-labelled Sp2/0 cells, both target and effector cells were shown to undergo cytolysis. Direct observation of target and effector cells co-incubated after labelling with different fluorescent dyes demonstrated that lysis correlates with the fusion of B cells and MHV-infected cells. These findings are consistent with the idea that the E2 protein of MHV, which is expressed on the infected cell surface and has receptor and membrane-fusion activities at neutral pH, selectively mediates fusion with cells of B lymphocyte lineage. This may represent a general mechanism by which enveloped viruses with fusion proteins that function at neutral pH can interfere with the function of subsets of immune cells.

Animals↗