A dominant idiotype in the antibody response against the influenza virus hemagglutinin. Serum and in situ analyses

PY206 is an Id associated with a BALB/c murine mAb described as being specific for the influenza A virus hemagglutinin. However, production of this Id by BALB/c mice immunized with influenza is low. This report shows that the PY206 Id is a dominant component of the anti-influenza antibody response in C57BL/6J strain mice infected intranasally with the influenza A/Hong Kong/168/(H3N2)[R] X-31 virus. High PY206 Id expression was linked to the IgHb Ig allotype locus. PY206 Id+ antibody-forming cells were identified in situ in cryostat sections of lymphoid tissues and idiotypic heterogeneity was identified among PY206+ B cells. Uninfected adult C57BL/6J mice had PY206 Id in their serum that lacked influenza binding specificity. In situ analysis of prenatal and neonatal spleen of uninfected C57BL/6J mice showed that the expansion of PY206 Id+ B cells occurred early in development. PY206+ cells were demonstrated in the lungs of influenza-infected mice but not in normal mice, establishing the capability to study this B cell population in the lung. This model offers the opportunity to manipulate the anti-influenza A virus hemagglutinin B cell response and to study the proliferation and migration of influenza-specific B cells in their native tissue environments.     

Ly-1 B helper cells in autoimmune "viable motheaten" mice

Previous work has demonstrated that Ly-1 B cells from normal C57BL/6J mice help the response of B cell subsets to the 4-hydroxy-3-nitrophenylacetyl hapten (NP). This regulatory cell population, called BH, preferentially helps the expression of plaque-forming B cells which express a predominant set of serologically related determinants collectively known as the NPb idiotype family. The specificity of BH cell activity in the NP system is a reflection of NPb idiotype-specific BH cell surface receptors. Thus, BH cells recognize autologous (i.e., idiotype) antigens. Given these observations and previous associations of increased Ly-1 B cell frequency in autoimmune mice, it was hypothesized that autoreactive Ly-1 BH cells may be present in high frequencies and in an activated state in autoimmune mice. To test this hypothesis the immunologic activity of BH cells in autoimmune viable motheaten (mev/mev) mice was studied. It was determined that splenic BH cells are approximately 10 times more frequent in viable motheaten than normal mice. The fact that BH cells from viable motheaten mice are activated was suggested by the presence of NPb idiotype-specific BH replacing helper activity in sera or B cell supernatants from these autoimmune mice. The soluble helper activities constitutively produced in mev/mev splenic B cell cultures and detected in mev/mev serum were resolved into two moieties, an NPb idiotype-specific immunoglobulin and a nonimmunoglobulin lymphokine(s) fraction. Purified mev/mev B cell-derived B cell maturation factor could substitute for the lymphokine moiety in the NPb idiotype helper cell assay. These results suggest that at least two signals, anti-idiotype immunoglobulin and a late-acting B cell maturation factor, are required for BH-dependent helper activity. The relationships of these results to current concepts of B cell activation mechanisms and the possible association of Ly-1 BH cells with autoimmunity are discussed.     

Control of the specificity of T cell-mediated anti-idiotype immunity by natural regulatory T cells

The idiotypes of B cell lymphomas represent tumor-specific antigens. T cell responses induced by idiotype vaccination in vivo are directed predominantly against CDR peptides, whereas in vitro T cells also recognize framework-derived epitopes. To investigate the mechanisms regulating the specificity of idiotype-specific T cells, BALB/c or B10.D2 mice were immunized with mature dendritic cells loaded with H-2K^d-restricted peptides from influenza hemagglutinin, or from shared (J region) or unique (CDR3) structures of the A20 lymphoma idiotype. Antigen-specific T cells were induced in vivo by the CDR3 and influenza epitopes, but not by the J peptide. Gene expression profiling of splenic regulatory T cells revealed vaccination-induced Treg activation and proliferation. Treg activity involved J epitope-dependent IL-10 secretion and functional suppression of peptide-specific effector T cells. Vaccination-induced in vivo proliferation of transgenic hemagglutinin-specific T cells was suppressed by co-immunization with the J peptide and was restored in CD25-depleted animals. In conclusion, Treg induced by a shared idiotype epitope can systemically suppress T cell responses against idiotype-derived and immunodominant foreign epitopes in vivo. The results imply that tumor vaccines should avoid epitopes expressed by normal cells in the draining lymph node to achieve optimal anti-tumor efficacy.     

Age-related changes in T cell function.

A comparison was made of the abilities of carrier (BGG)-primed T cell populations from young (4-month old), middle-aged (14- and 19-month old) and old (31- and 34-month old) mice to collaborate with hapten (DNP)-primed B cells from young mice in a cell-transfer system. The plaque-forming cell responses to 2,4-dinitrophenol (DNP) were measured by a modification of the Jerne plaque assay. The DNP-specific antibody-forming cell responses of old T cell/young B cell combinations were significantly lower than those of young T cell/young B cell combinations, both in the number of T cells needed for peak response and in the size of that response. These data indicate that the primed T cell populations of old mice are deficient by a factor of 6 in their ability to initiate B cell proliferation and differentiation into antibody-forming cells.     

Cellular immune responses of mice to influenza virus infection

Mice infected with influenza virus develop cytotoxic T lymphocytes (CTL) specific for viral antigens prior to the appearance of virus-specific antibody-forming cells (AFCs). Effector T cells were detected at a time coincident with a precipitous decline in pulmonary virus titer. CTLs of draining lymph nodes and spleen were found to be cross-reactive among H-2 compatible cells infected with influenza type A virus subtypes. AFCs were observed to be primarily hemagglutinin specific. Virus-specific IgA-secreting AFCs were detected in mediastinal lymph nodes of infected mice.     

Lymphotoxin-alpha-deficient mice make delayed,but effective,T and B cell responses to influenza

Lymphotoxin-alpha(-/-) (LTalpha(-/-)) mice are thought to be unable to generate effective T and B cell responses. This is attributed to the lack of lymph nodes and the disrupted splenic architecture of these mice. However, despite these defects we found that LTalpha(-/-) mice could survive infection with a virulent influenza A virus. LTalpha(-/-) mice and normal wild-type mice infected with influenza A generated similar numbers of influenza-specific CD8 T cells that were able to produce IFN-gamma and kill target cells presenting influenza peptides. Furthermore influenza-infected LTalpha(-/-) mice produced high titers of influenza-specific IgM, IgG, and IgA. However, both CD8 and B cell immune responses were delayed in LTalpha(-/-) mice by 2-3 days. The delayed cellular and humoral immune response was sufficient to mediate viral clearance in LTalpha(-/-) mice that were infected with relatively low doses of influenza virus. However, when LTalpha(-/-) mice were infected with larger doses of influenza, they succumbed to infection before the immune response was initiated. These results demonstrate that neither LTalpha nor constitutively organized lymphoid tissues, such as lymph nodes and spleen, are absolutely required for the generation of effective immunity against the respiratory virus influenza A. However, the presence of LTalpha and/or lymph nodes does accelerate the initiation of immune responses, which leads to protection from larger doses of virus.     

Heterosubtypic immunity to influenza A virus in mice lacking IgA, all Ig, NKT cells, or gamma delta T cells

The mechanisms of broad cross-protection to influenza viruses of different subtypes, termed heterosubtypic immunity, remain incompletely understood. We used knockout mouse strains to examine the potential for heterosubtypic immunity in mice lacking IgA, all Ig and B cells, NKT cells (CD1 knockout mice), or gamma(delta) T cells. Mice were immunized with live influenza A virus and compared with controls immunized with unrelated influenza B virus. IgA(-/-) mice survived full respiratory tract challenge with heterosubtypic virus that was lethal to controls. IgA(-/-) mice also cleared virus from the nasopharynx and lungs following heterosubtypic challenge limited to the upper respiratory tract, where IgA has been shown to play an important role. Ig(-/-) mice controlled the replication of heterosubtypic challenge virus in the lungs. Acute depletion of CD4+ or CD8+ T cell subsets abrogated this clearance of virus, thus indicating that both CD4+ and CD8+ T cells are required for protection in the absence of Ig. These results in Ig(-/-) mice indicate that CD4+ T cells can function by mechanisms other than providing help to B cells for the generation of Abs. Like wild-type mice, CD1(-/-) mice and gamma(delta) (-/-) mice survived lethal heterosubtypic challenge. Acute depletion of CD4+ and CD8+ cells abrogated heterosubtypic protection in gamma(delta) (-/-) mice, but not B6 controls, suggesting a contribution of gamma(delta) T cells. Our results demonstrate that the Ab and cellular subsets deficient in these knockout mice are not required for heterosubtypic protection, but each may play a role in a multifaceted response that as a whole is more effective than any of its parts.     

A dominant Th epitope in influenza nucleoprotein. Analysis of the fine specificity and functional repertoire of T cells recognizing a single determinant.

The sequence 260-283 of the nucleoprotein (NP) of influenza A virus is an epitope recognized by virus-immune lymph node cells from CBA (H-2k), B6 (H-2b), and B10.S (H-2s) mice. Further analysis shows that there are at least two Th epitopes within this sequence: the one close to the N-terminal (p260-273) is recognized by T cells from CBA and B6 mice while that close to the carboxyl-terminal (p270-283) is a dominant Th determinant in B10.S mice. The fine specificity of the recognition of this epitope by NP-specific T cell clones is also studied. When B10.S mice were infected intranasally or i.v. with live influenza virus, or immunized by different ways with various Ag preparations, P270-283 persistently emerged as a dominant T cell epitope. Immunization of B10.S mice with peptide p270-283 induces T cells with different in vivo functions including class II-restricted cytotoxicity, cognate help for Ag-specific antibody synthesis and delayed type hypersensitivity. This may have important implications for the understanding of the differentiation and classification of subsets of CD4+ T cells. The corresponding sequence of the NP of an equine influenza virus, A/Eq/Prague/56, which has a substitution (leucine to proline) at position 283, was not recognized by the lymph node cells from mice primed with either A/Okuda or A/Eq/Prague. However, the peptide, p270-283(E), representing this sequence induced T cell responses to both human and equine viruses. The data are discussed with respect to the development of viral vaccines.     

Impact of ageing on the response and repertoire of influenza virus-specific CD4 T cells

Background

Ageing has been shown to reduce CD8 T cell repertoire diversity and immune responses against influenza virus infection in mice. In contrast, less is known about the impact of ageing on CD4 T cell repertoire diversity and immune response to influenza virus infection.

Results

The CD4 T cell response was followed after infection of young and aged C57BL/6 mice with influenza virus using a tetramer specific for an immunodominant MHC class II epitope of the influenza virus nucleoprotein. The appearance of virus-specific CD4 T cells in the lung airways of aged mice was delayed compared to young mice, but the overall peak number and cytokine secretion profile of responding CD4 T cells was not greatly perturbed. In addition, the T cell repertoire of responding cells, determined using T cell receptor Vβ analysis, failed to show the profound effect of age we previously described for CD8 T cells. The reduced impact of age on influenza-specific CD4 T cells was consistent with a reduced effect of age on the overall CD4 compared with the CD8 T cell repertoire in specific pathogen free mice. Aged mice that were thymectomized as young adults showed an enhanced loss of the epitope-specific CD4 T cell response after influenza virus infection compared with age-matched sham-thymectomized mice, suggesting that a reduced repertoire can contribute to impaired responsiveness.

Conclusions

The diversity of the CD4 T cell repertoire and response to influenza virus is not as profoundly impaired by ageing in C57BL/6 mice as previously shown for CD8 T cells. However, adult thymectomy enhanced the impact of ageing on the response. Understanding the impact of ageing on CD4 T cell responses to influenza virus infection is an important prerequisite for developing better vaccines for the elderly.

     

The human and murine influenza-specific B cell repertoires share a common idiotope

We have dissected the human influenza-specific B cell repertoire by performing Epstein-Barr virus (EBV) limiting dilution analysis of lymphocytes obtained from donors before and after immunization with a commercially available influenza vaccine. In addition to an analysis of precursor frequency and light chain diversity, we studied sera and culture supernatants containing human anti-influenza antibodies with a panel of murine monoclonal antibodies specific for idiotopes identified on murine anti-PR8 and anti-X-31 antibodies. An idiotypic specificity present on the X-31-specific murine monoclonal PY206 has previously been shown to be shared by murine antibodies specific for PR8, X-31, and other influenza viruses. We observed little correlation among the following parameters: anti-viral titer, serum idiotope content, precursor frequency and immune status. More interestingly, there was a striking predominance of human influenza-specific antibodies that utilized lambda light chains. In addition, 12 of 26 human anti-influenza monoclonals strongly inhibited the binding of one of the murine anti-idiotopes to the labeled murine antibody, PY206. This is the same idiotope that is shared among murine antiinfluenza antibodies and all six individuals studied contained clones reactive with this anti-idiotope. Seven of these 12 idiotope-positive human antibodies gave partial cross-reactivity in a second anti-idiotypic system. These observations imply that a significant level of homology exists between the binding sites of human and murine influenza-specific antibodies and suggest that idiotypic manipulation of the human immune response to influenza virus may have important therapeutic implications.     

Regulation of T15 idiotype dominance. I. Mice expressing the xid immune defect provide normal help to T15+ B cell precursors

The immune response to phosphocholine (PC) in many strains of mice is dominated by the T15 idiotype family of anti-PC antibodies. By introducing the CBA/N X-linked immune defect (xid gene) into these mice, one profoundly alters their ability to make a T15-predominant, IgM anti-PC response. This loss of T15 dominance in mice expressing the xid gene is not due to the presence of suppressor T cells or the lack of T15 idiotype-specific helper cells in these mice. Thus, one can reconstitute a T15 idiotype-dominant response in immune defective mice with B cells from normal mice, and in adoptive transfer assays the primed T helper cells from immune-defective mice provide qualitatively the same help to normal B cells as the T helper cells from normal mice. T15 idiotype dominance appears to be controlled by the expression and activation of Lyb-5+ PC-specific B cells. Thus, the majority of T15+ B cell precursors are restricted to this B cell subset, whereas the Lyb-5- B cell subset contains predominantly T15-, anti-PC B cell precursors, which produce mainly IgG antibodies after activation by PC-containing antigens.     

Enhancement of the immune response to surface antigens of the influenza B virus as a result of their covalent binding with a synthetic polymer carrier

The primary immune response (the number of antibody-forming cells, AFC) and the delayed type hypersensitivity (DTHS) were studied in mice immunized either with isolated glycoproteins of influenza virus (hemagglutinin, HA and HA plus neuraminidase, HA plus NA) or with their conjugates with an acrylic acid copolymer (CP) and N-vinylpyrrolidone of equimolar composition. Immunization of mice with conjugates containing virus proteins (virogates-HA-CP or HA plus NA-CP--entailed a 50-100 increment of the number of IgM- and IgG-AFC, anti-HA as compared with analogous parameters during immunization of animals with isolated virus proteins. Immunization of mice with the virogate HA-CP gives rise to the development of a more pronounced DTHS to HA. The authors discuss the possibility of the use of this basically new approach to the design of highly immunogenous vaccine preparations, effective in the control of influenza and other virus diseases.     

Immune Response against Hamster Erythrocytes in the Low-Responder Mouse Strains

Patterns of proliferation of antibody-forming cells after an intravenous immunization with hamster erythrocytes (HRBC) were compared in groups of mice possessing different activities of thymus-derived lymphocytes (T cells). 1) Marked differences in the numbers of hemolysin plaque-forming cells (PFC) after HRBC injection were found among the low- and high-responder normal mice and those pretreated with HRBC in complete Freund's adjuvant (CFA) or incomplete adjuvant (IFA), and they appeared to depend primarily upon the different rates of proliferation of antibody-forming cells rather than on the numbers of antigen-specific lymphocytes initiating the antibody response. 2) The numbers of hemolytic foci were slightly larger in mice with large numbers of PFC (normal SL mice, the pretreated SL and C57BL/6 mice) than in those with small numbers of PFC (normal C57BL/6 mice). The numbers of hemolytic foci increased at almost the same rate from day 2 to day 3 in both groups, while the numbers of PFC increased more efficiently in mice with large numbers of PFC than in those with small numbers of PFC from day 2 to day 3. Individual hemolytic foci appeared to contain larger numbers of PFC in mice with large total numbers of PFC than in those with small total numbers of PFC. 3) The numbers of rosette-forming cells (RFC) were increased by pretreatment with HRBC in CFA and by pretreatment with HRBC in IFA to almost the same extent. Rates of increases in PFC were, however, larger by pretreatment with HRBC in CFA than with HRBC in IFA. These results suggested that the activity of the T cell determined not only the rates of proliferation of antibody-forming cells but also the antibody-producing capacity of each cell.     

A study of the functional capabilities of human neonatal lymphocytes for in vitro specific antibody production

The ability of neonatal B and T cells to participate in the in vitro production of anti-influenza virus antibody was studied. Peripheral blood mononuclear cells from nearly all normal adults produce anti-influenza virus antibody when stimulated in vitro with type A influenza virus. Cord blood mononuclear cells, however, consistently failed to do so. Using Epstein-Barr virus activation or coculture with irradiated adult T cells in the presence of influenza virus to identify precursor B cells for anti-viral antibody production, newborns were found to have a decreased number of influenza-specific B cells as compared with adults. Thus, a paucity of precursor B cells for anti-influenza virus antibody was one factor contributing to the absent in vitro antibody response. Additional studies were undertaken to investigate the capabilities of newborn T cells in the in vitro response to influenza virus. Newborn T cells failed to proliferate when cultured with influenza virus. Irradiated newborn T cells were, however, able to provide help for specific antibody production in influenza virus-stimulated cocultures with allogeneic adult B cells, and newborn T cells proliferated when stimulated with alloantigens; their helper function in allogeneic coculture was, thus, likely mediated by T cells stimulated by alloantigens rather than by influenza virus. In the absence of T cell irradiation, no antibody was produced in cocultures of adult B cells and neonatal T cells, at least in part as the result of a radiosensitive suppressor T cell. Suppression in influenza virus-stimulated allogeneic cocultures was also observed with normal adult T cells and is, therefore, a property of both newborn and adult T cells. Thus, allogeneic help and suppression can both be manifested in exogenous antigen-stimulated allogeneic cocultures. In addition, both of these allogeneic effects can be mediated by neonatal T cells, indicating that these functions are present at the time of birth and do not require previous exogenous antigenic exposure for expression.     

Influenza virus-induced interferon production in mouse spleen cell culture: T cells as the main producer.

Interferon production by spleen cells from unimmunized C3H mice challenged in vitro with influenza virus AO/PR8 was investigated. Glass-nonadherent cells (lymphocytes) produced significant levels of interferon, although cocultivation of glass-adherent macrophages was needed for optimal production. Treatment of the cells with antithymocyte serum and complement markedly reduced the interferon production. When glass-nonadherent cells were fractionated on a nylon wool column, the T-cell-enriched fraction consistently produced more interferon than the B-cell-enriched fraction. It is concluded that T cells are an important producer of interferon in spleen cell cultures from normal mice upon challenge with influenza virus, although non-T cells (macrophages and B cells) also may produce interferon under suitable conditions.     

Naturally occurring cytotoxic T lymphocyte precursors with specificity for an Ig idiotype

The humoral response to the p-azobenzenearsonate hapten in the A/J mouse includes the major cross-reactive idiotype associated with anti-p-azobenzenearsonate (CRIA) found in all immunized mice. Limiting dilution cultures of non-immunized spleen cells of A/J mice with irradiated B hybridoma cells bearing the Ig idiotype, CRIA, in the presence of T cell growth factors developed cytotoxic activity against the CRIA-bearing hybridoma; in some wells this activity was completely abrogated by an anti-idiotype mAb specific for CRIA or by a univalent hapten antigen, tyrosine-p-azobenzenearsonate, indicating the existence of cytotoxic T cell precursors (CTL-P) specific for one or more idiotopes of CRIA in normal spleen cells. The CTL clones lysed targets in a H-2D-restricted manner and were cytotoxic for CRIA-bearing hybridoma lines, but not for CRIA-non-bearing, IgG1k-bearing hybridoma lines. These CTL-P were detected at a high frequency (1/4,500 to 1/10,000) in a spleen cell population of non-immunized, relatively aged A/J mice (16 to 30 wk of age), and at a lower frequency in spleen cells of younger A/J mice (8 wk of age). However, they were not detected in normal spleen cells of B10.A (CRIA-non-producer) mice at any age (less than 1/6 x 10(5)). Normal Ighd-congenic C.AL-20 mice (16 wk of age), that are CRIA producers had as a high frequency of the CTL-P as did A/J mice, whereas normal Ighb-congenic C.B-20 mice (CRIA-non-producers) had none. In the spleen cells of the CRIA-producers, cytotoxicity of the CTL-P developed only in cultures with small numbers of seeding cells. They were completely absent in cultures with greater numbers of cells; this may be due to the presence of suppressor cells of lower frequency but greater potency. In lymph node cells or PBL of relatively aged A/J mice, the CTL-P were also detected, but only in cultures containing higher cell numbers, and at low frequency (between 1/5 x 10(5) to 1/2 x 10(6)). In thymocytes of 8-wk-old A/J mice, they were occasionally detected at very low frequency (less than or equal to 1/1 x 10(6)), but were not present in the bone marrow cells at any age. These results demonstrate the high incidence of the generation of CTL-P specific for an autologous Ag, and indicate that CRIA on B cells may induce CTL specific for CRIA. However, the development of CTL-P may be inhibited by co-existent suppressor cells under normal conditions.     

Potential Role of HPA Axis and Sympathetic Nervous Responses in Depletion of B Cells Induced by H9N2 Avian Influenza Virus Infection

Except severe pulmonary disease caused by influenza virus infection, an impaired immune system is also a clinic characteristic. However, the mechanism(s) of influenza virus infection-induced depletion of B cells was unknown. Here, we compared the effect of two variant virulence H9N2 virus infections on mouse B cells. Our study found that the infection with highly pathogenic virus (V) of led to depletion of spleen B cells and bone marrow (BM) early B cells, compared to lowly pathogenic virus (Ts). Moreover, high apoptosis and cell cycle arrest in spleen and BM were detected, suggesting important factors for the reduction of B cells in both organs. Further, this effect was not caused by virus replication in spleen and BM. Compared to Ts virus infection, V virus resulted in higher glucocorticoids (GCs) and lower leptin level in plasma. Intraperitoneal GCs receptor antagonist RU486 injection was sufficient to prevent the loss of spleen B cell and BM pro- and immature B cells, but similar result was not observed in leptin-treated mice. Depletion of spleen B cells and BM pro-B cells was also reversed by chemical sympathectomy mediated by the norepinephrine (NE) analog 6-hydroxydopamine (6-OHDA), but the treatment didn''t affect the GCs level. This study demonstrated that depletion of B cells induced by H9N2 AIV was dependent on HPA axis and sympathetic response.     

Mice can recover from pulmonary influenza virus infection in the absence of class I-restricted cytotoxic T cells.

Intranasal exposure of athymic (nu/nu) BALB/c mice to influenza virus leads to a persistent infection of the respiratory tract from which the mice die, usually within 3 to 4 wk with symptoms of general cachexia. However, if these nude mice were injected 1 day after infection, with approximately 10(6) cells from individual virus-specific MHC class II-restricted Th cell clones, they showed greatly reduced mortality and the titers of infectious virus in their lungs were reduced, often to undetectable levels. By coinfecting mice with pairs of antigenically distinct viruses and subsequently determining the extent of clearance of each type of virus, it could be shown first that the clearance mechanism was immunologically specific but did not display the typical crossreaction of class I-restricted cytotoxic T (Tc) cells. In addition, neither primary nor memory Tc responses could be detected in these mice. Second, Th cell clones promoted clearance solely of those viruses that contained the specific Th cell determinant, i.e., Th cell-nonreactive bystander viruses were not cleared. These findings were compatible with virus clearance being effected either directly after recognition of infected class II-positive cells by the transferred Th cells or indirectly via promotion of a glycoprotein-specific antibody response. The latter seems to be the case because transfer of Th cells into infected T and B cell-deficient SCID mice did not result in virus clearance, although transfer of an anti-hemagglutinin antibody cocktail did. Thus, a virus-specific Tc cell response is not a requirement for recovery from a pulmonary influenza virus infection.     

Modulation of SLE induction in naive mice by specific T cells with suppressor activity to pathogenic anti-DNA idiotype.

T cells (CD8+) with specific suppressor activity against anti-dsDNA antibody (16/6 Id+) were generated in vitro. The cells were established from BALB/c-enriched T cells exposed in vitro to silica beads coated with the pathogenic anti-DNA idiotype, 16/6. The idiotype specificity of the suppressor cells was demonstrated by (a) specific induction of a decrease in proliferative response of T helper cell lines specific for the pathogenic idiotype (16/6 Id), when exposed to the idiotype, with no effect on T cell lines with other specificities, e.g., against human IgM or synthetic polypeptide. (b) Effectively suppressing in vitro antibody production of anti-16/6 antibody, employing 16/6-primed B cells and specific helper T cell line. The 16/6 Id-specific Ts cells were found to be MHC restricted. Weekly intravenous injections of 10(7) 16/6 Id-specific Ts cells given to BALB/c mice at different stages of experimental SLE disease prevented the clinical, serological, and pathological manifestations. This effect was characterized by decreased titers of autoantibodies (e.g., anti-DNA, anti-Sm antibodies) in the sera, by abolishment of the proteinuria, leukopenia, and the increased ESR, followed by decreased immunoglobulin deposition in the kidneys. Treating the mice with control IgM-specific T cells did not affect the above parameters. These studies demonstrate the ability to generate Ts cells specific for pathogenic idiotypes. The method might be employed therapeutically to modulate the course of autoimmune conditions.     

Influenza virus-induced type I interferon leads to polyclonal B-cell activation but does not break down B-cell tolerance

The link between infection and autoimmunity is not yet well understood. This study was designed to evaluate if an acute viral infection known to induce type I interferon production, like influenza, can by itself be responsible for the breakdown of immune tolerance and for autoimmunity. We first tested the effects of influenza virus on B cells in vitro. We then infected different transgenic mice expressing human rheumatoid factors (RF) in the absence or in the constitutive presence of the autoantigen (human immunoglobulin G [IgG]) and young lupus-prone mice [(NZB x NZW)F(1)] with influenza virus and looked for B-cell activation. In vitro, the virus induces B-cell activation through type I interferon production by non-B cells but does not directly stimulate purified B cells. In vivo, both RF and non-RF B cells were activated in an autoantigen-independent manner. This activation was abortive since IgM and IgM-RF production levels were not increased in infected mice compared to uninfected controls, whether or not anti-influenza virus human IgG was detected and even after viral rechallenge. As in RF transgenic mice, acute viral infection of (NZB x NZW)F(1) mice induced only an abortive activation of B cells and no increase in autoantibody production compared to uninfected animals. Taken together, these experiments show that virus-induced acute type I interferon production is not able by itself to break down B-cell tolerance in both normal and autoimmune genetic backgrounds.