The role of NK cells in the development of autoantibodies

The systemic lupus erythematosus (Sle1) interval from the NZM2410 mouse strain has been shown to be responsible for high levels of autoantibody production against antinuclear antibodies (ANA) when transferred into C57BL/6 mice. B cells derived from the B6.Sle1 strain are required for the production but help from both T-dependent and independent sources have been documented. Using radiation chimeras constructed in a strain of mice that is chronically depleted of Natural killer (NK) cells, but not NKT cells, we have examined the role of NK cells in the development of ANA in this context. Our results show that in the presence of intact T cell help depletion of NK cells does not affect ANA production. However, when T cell help is compromised, the prevalence of animals producing ANA is significantly decreased suggesting that NK cells can provide help for the T-independent production of ANA. Further experiments provide a possible mechanism for the NK-cell dependence.     

Antigen-specific responses and ANA production in B6.Sle1b mice: A role for SAP

B6.Sle1b mice, which contain the Sle1b gene interval derived from lupus prone NZM2410 mice on a C57BL/6 background, present with gender-biased, highly penetrant anti-nuclear antibody (ANA) production. To obtain some insight into the possible induction mechanism of autoantibodies in these mice we compared antigen-specific T dependent (TD) and T independent (TI-II) responses between B6.Sle1b and B6 mice before the development of high ANA titers. Our results show that B6.Sle1b mice mount enhanced responses to a TI-II antigen. Additionally, the memory T cell response generated by a TD antigen also increased. This enhancement correlates with the greater ability of B cells from B6.Sle1b mice to present antigen to T cells. The SLAM Associated Protein (SAP) is critical for signaling of many of the molecules encoded by the SLAM/CD2 gene cluster, candidates for mediating the Sle1b phenotype; therefore, we also investigated the effect of sap deletion in these strains on the TD and TI-II responses as well as on ANA production. The results of these studies of responses to non-self-antigens provide further insight into the mechanism by which responses to self-antigens might be initiated in the context of specific genetic alterations.     

Antigen-specific responses and ANA production in B6.Sle1b mice: a role for SAP

B6.Sle1b mice, which contain the Sle1b gene interval derived from lupus prone NZM2410 mice on a C57BL/6 background, present with gender-biased, highly penetrant anti-nuclear antibody (ANA) production. To obtain some insight into the possible induction mechanism of autoantibodies in these mice we compared antigen-specific T dependent (TD) and T independent (TI-II) responses between B6.Sle1b and B6 mice before the development of high ANA titers. Our results show that B6.Sle1b mice mount enhanced responses to a TI-II antigen. Additionally, the memory T cell response generated by a TD antigen also increased. This enhancement correlates with the greater ability of B cells from B6.Sle1b mice to present antigen to T cells. The SLAM Associated Protein (SAP) is critical for signaling of many of the molecules encoded by the SLAM/CD2 gene cluster, candidates for mediating the Sle1b phenotype; therefore, we also investigated the effect of sap deletion in these strains on the TD and TI-II responses as well as on ANA production. The results of these studies of responses to non-self-antigens provide further insight into the mechanism by which responses to self-antigens might be initiated in the context of specific genetic alterations.     

The development of autoimmune features in aging mice is closely associated with alterations of the peripheral CD4+ T‐cell compartment

Some signs of potential autoimmunity, such as the appearance of antinuclear antibodies (ANAs) become prevalent with age. In most cases, elderly people with ANAs remain healthy. Here, we investigated whether the same holds true for inbred strains of mice. Indeed, we show that most mice of the C57BL/6 (B6) strain spontaneously produced IgG ANA at 8–12 months of age, showed IgM deposition in kidneys and lymphocyte infiltrates in submandibular salivary glands. Despite all of this, the mice remained healthy. ANA production is likely CD4⁺ T‐cell dependent, since old (40–50 weeks of age) B6 mice deficient for MHC class II do not produce IgG ANAs. BM chimeras showed that ANA production was not determined by age‐related changes in radiosensitive, hematopoietic progenitor cells, and that the CD4⁺ T cells that promote ANA production were radioresistant. Thymectomy of B6 mice at 5 weeks of age led to premature alterations in T‐cell homeostasis and ANA production, by 15 weeks of age, similar to that in old mice. Our findings suggest that a disturbed T‐cell homeostasis may drive the onset of some autoimmune features.     

Ly108 expression distinguishes subsets of invariant NKT cells that help autoantibody production and secrete IL-21 from those that secrete IL-17 in lupus prone NZB/W mice

Lupus is a systemic autoimmune disease characterized by anti-nuclear antibodies in humans and genetically susceptible NZB/W mice that can cause immune complex glomerulonephritis. T cells contribute to lupus pathogenesis by secreting pro-inflammatory cytokines such as IL-17, and by interacting with B cells and secreting helper factors such as IL-21 that promote production of IgG autoantibodies. In the current study, we determined whether purified NKT cells or far more numerous conventional non-NKT cells in the spleen of NZB/W female mice secrete IL-17 and/or IL-21 after TCR activation in vitro, and provide help for spontaneous IgG autoantibody production by purified splenic CD19⁺ B cells. Whereas invariant NKT cells secreted large amounts of IL-17 and IL-21, and helped B cells, non-NKT cells did not. The subset of IL-17 secreting NZB/W NKT cells expressed the Ly108^loCD4⁻NK1.1⁻ phenotype, whereas the IL-21 secreting subset expressed the Ly108^hiCD4⁺NK1.1⁻ phenotype and helped B cells secrete a variety of IgG anti-nuclear antibodies. α-galactocylceramide enhanced the helper activity of NZB/W and B6.Sle1b NKT cells for IgG autoantibody secretion by syngeneic B cells. In conclusion, different subsets of iNKT cells from mice with genetic susceptibility to lupus can contribute to pathogenesis by secreting pro-inflammatory cytokines and helping autoantibody production.     

Selenium supplementation suppresses immunological and serological features of lupus in B6.Sle1b mice

Systemic lupus erythematosus (SLE) is a debilitating multi-factorial immunological disorder characterized by increased inflammation and development of anti-nuclear autoantibodies. Selenium (Se) is an essential trace element with beneficial anti-cancer and anti-inflammatory immunological functions. In our previous proteomics study, analysis of Se-responsive markers in the circulation of Se-supplemented healthy men showed a significant increase in complement proteins. Additionally, Se supplementation prolonged the life span of lupus prone NZB/NZW-F1 mice. To better understand the protective immunological role of Se in SLE pathogenesis, we have investigated the impact of Se on B cells and macrophages using in vitro Se supplementation assays and the B6.Sle1b mouse model of lupus with an oral Se or placebo supplementation regimen. Analysis of Se-treated B6.Sle1b mice showed reduced splenomegaly and splenic cellularity compared to untreated B6. Sle1b mice. A significant reduction in total B cells and notably germinal center (GC) B cell numbers was observed. However, other cell types including T cells, Tregs, DCs and pDCs were unaffected. Consistent with reduced GC B cells there was a significant reduction in autoantibodies to dsDNA and SmRNP of the IgG2b and IgG2c subclass upon Se supplementation. We found that increased Se availability leads to impaired differentiation and maturation of macrophages from mouse bone marrow derived progenitors in vitro. Additionally, Se treatment during in vitro activation of B cells with anti-CD40L and LPS inhibited optimal B cell activation. Overall our data indicate that Se supplementation inhibits activation, differentiation and maturation of B cells and macrophages. Its specific inhibitory effect on B cell activation and GC B cell differentiation could be explored as a potential therapeutic supplement for SLE patients.     

Lack of T cells in Act1-deficient mice results in elevated IgM-specific autoantibodies but reduced lupus-like disease

Act1 is a negative regulator of B‐cell activation factor of the TNF family (BAFF) and CD40L‐induced signaling. BALB/C mice lacking Act1 develop systemic autoimmunity resembling systemic lupus erythematosus (SLE) and Sjögren's syndrome (SjS). SLE and SjS are characterized by anti‐nuclear IgG autoantibody (ANA‐IgG) production and inflammation of peripheral tissues. As autoantibody production can occur in a T‐cell dependent or T‐cell independent manner, we investigated the role of T‐cell help during Act1‐mediated autoimmunity. Act1‐deficiency was bred onto C57Bl/6 (B6.Act1^?/?) mice and B6.TCRβ^?/?TCRδ^?/?Act1^?/? (TKO) mice were generated. While TCRβ/δ‐sufficient B6.Act1^?/? mice developed splenomegaly and lymphadenopathy, hypergammaglobulinemia, elevated levels of ANA‐IgG, and kidney pathology, TKO mice failed to develop any such signs of disease. Neither B6.Act1^?/? nor TKO mice developed SjS‐like disease, suggesting that epigenetic interactions on the BALB/C background are responsible for this phenotype in BALB/C.Act1^?/? mice. Interestingly, BAFF‐driven transitional B‐cell abnormalities, previously reported in BALB/C.Act1^?/? mice, were intact in B6.Act1^?/? mice and largely independent of T cells. In conclusion, T cells are necessary for the development of SLE‐like disease in B6.Act1^?/? mice, but not BAFF‐driven transitional B‐cell differentiation.     

Systemic IFN-alpha drives kidney nephritis in B6.Sle123 mice

The impact of IFN-alpha secretion on disease progression was assessed by comparing phenotypic changes in the lupus-prone B6.Sle1Sle2Sle3 (B6.Sle123) strain and the parental C57BL/6 (B6) congenic partner using an adenovirus (ADV) expression vector containing a recombinant IFN-alpha gene cassette (IFN-ADV). A comprehensive comparison of cell lineage composition and activation in young B6 and B6.Sle123 mice revealed a variety of cellular alterations in the presence and absence of systemic IFN-alpha. Most IFN-alpha-induced phenotypes were similar in B6 and B6.Sle123 mice; however, B6.Sle123 mice uniquely exhibited increased B1 and plasma cells after IFN-alpha exposure, although both strains had an overall loss of mature B cells in the bone marrow, spleen and periphery. Although most of the cellular effects of IFN-alpha were identical in both strains, severe glomerulonephritis occurred only in B6.Sle123 mice. Mice injected with IFN-ADV showed an increase in immune complex deposition in the kidney, together with an unexpected decrease in serum anti-nuclear antibody levels. In summary, the predominant impact of systemic IFN-alpha in this murine model is an exacerbation of mechanisms mediating end organ damage.     

In Vivo Generation of Mouse Natural Killer Cells: Role of the Spleen and Thymus

The role of the spleen and thymus was investigated in the natural killer (NK) cell system. These NK cells have the ability to kill a variety of tumour cells as demonstrated in vitro in short-term ⁵¹Cr release assays. The work presented deals with three observations: (1) the effect of splenectomy on the levels of NK activity in the blood and lymph nodes. (2) the effect of splenectomy on the reconstitution of irradiated animals with bone marrow cells, and (3) the level of NK activity in adult thymectomized, irradiated animals which were reconstituted with bone marrow or thymus cells from either high or low NK activity animals. Thus, for the third point, chimaeras were established between histocompatible strains of mice A. BY (a low NK strain), and C57B1/6 (a high NK strain). The ability of T cells from one strain could then be observed to either help or suppress the NK activity of the bone-marrow-derived cells. The data presented show that the absence of a spleen does not affect MK activity or reconstitution of NK cells in irradiated animals. Further, T cells from one strain do not affect NK activity of animals reconstituted with bone marrow cells from a histocompatible strain. Thus T cells from a low NK stain (A. BY) did not suppress the high activity of C57B1/6 cells, and, conversely, the C57B1/6 T cells did not compensate for the low NK activity of A. BY cells.     

Lupus resistance is associated with marginal zone abnormalities in an NZM murine model

The NZM2410 and NZM TAN (TAN) are two of 27 inbred strains derived from an intercross between the NZW and NZB strains. NZM2410 mice develop a highly penetrant lupus nephritis mediated by three susceptibility loci, Sle1, Sle2 and Sle3. These three loci have been combined on a C57BL/6 background in a triple congenic strain that reconstitutes the NZM2410 autoimmune phenotype. Remarkably, inspite of the presence of Sle1, Sle2 and Sle3, TAN mice display a mild autoimmune phenotype reminiscent of NZW. Contrary to the lupus-prone strains, the majority of TAN CD4(+) T cells are in a na?ve-inactivated stage. TAN mice show B-cell developmental abnormalities similar to lupus-prone mice, such an accumulation of transitional T1 cells and peritoneal B-1a cells. TAN mice show, however, a unique expansion of the splenic marginal zone, in which B cells express high levels of CD5 and CD9, fail to migrate to the follicles in response to LPS, and show sub-optimal binding of T-independent type 2 antigens. Therefore, TAN mice present a functional silencing of marginal zone B cells, which have been previously implicated with autoimmune process. The TAN strain thus provides a novel model for the analysis of the genetic determinants of B-cell autoreactivity.     

NK cells modulate the lung dendritic cell‐mediated Th1/Th17 immunity during intracellular bacterial infection

The impact of the interaction between NK cells and lung dendritic cells (LDCs) on the outcome of respiratory infections is poorly understood. In this study, we investigated the effect and mechanism of NK cells on the function of LDCs during intracellular bacterial lung infection of Chlamydia muridarum in mice. We found that the naive mice receiving LDCs from C. muridarum‐infected NK‐cell‐depleted mice (NK‐LDCs) showed more serious body weight loss, bacterial burden, and pathology upon chlamydial challenge when compared with the recipients of LDCs from infected sham‐treated mice (NK+LDCs). Cytokine analysis of the local tissues of the former compared with the latter exhibited lower levels of Th1 (IFN‐γ) and Th17 (IL‐17), but higher levels of Th2 (IL‐4), cytokines. Consistently, NK‐LDCs were less efficient in directing C. muridarum‐specific Th1 and Th17 responses than NK+LDCs when cocultured with CD4⁺ T cells. In NK cell/LDC coculture experiments, the blockade of NKG2D receptor reduced the production of IL‐12p70, IL‐6, and IL‐23 by LDCs. The neutralization of IFN‐γ in the culture decreased the production of IL‐12p70 by LDCs, whereas the blockade of TNF‐α resulted in diminished IL‐6 production. Our findings demonstrate that NK cells modulate LDC function to elicit Th1/Th17 immunity during intracellular bacterial infection.     

Diseases caused by reactions of T lymphocytes to incompatible structures of the major histocompatibility complex. IV. Autoantibodies to nuclear antigens.

We studied the requirements for induction of ANA formation in non-irradiated F1 hybrid mice undergoing a chronic graft-versus-host reaction (GVHR) after the injection of parental-strain lymphocytes. T lymphocytes in the donor cell inoculum were both needed and sufficient for the induction of ANA formation. For optimal ANA formation, the F1 recipient mice had to differ at H-2 from the parental donor strain. ANA belonged to the IgG1, IgG2, IgM and IgA (sub)classes of immunoglobulin. IgG ANA occurred in maximal serum titres of 1 in 5,120. ANA were not donor anti-host alloantibodies. At least some ANA were true autoantibodies, i.e. of F1 origin, because they carried the Ig allotypic markers characteristic of the F1 hybrid recipients. These findings are consistent with the concept that the pathogenic mechanism underlying autoantibody formation during the GVHR is an abnormal T-B-cell co-operation. In this process, donor T cells react against foreign histocompatibility antigens of the F1 recipient and generate non-specific help for B cells, including the autoreactive B cells.     

Natural killer T-cell populations in C57BL/6 and NK1.1 congenic BALB.NK mice-a novel thymic subset defined in BALB.NK mice

Natural killer (NK) T lymphocytes are a subpopulation of T lymphocytes regarded as early regulators of immune responses. The majority of NKT cells are restricted by the CD1d molecule. NKT cells have mostly been studied in one single mouse strain, C57BL/6 (B6), because of the absence of NK1.1 in other common mouse strains, and the lack of other reliable surface markers for CD1d-restricted cells. To investigate NKT cell subsets in a mouse strain of a genetic background different from B6, we have back-crossed the NKT cell marker NK1.1 from the B6 mouse to the BALB/c mouse strain. We show that NKT cells in the congenic BALB.B6-NK1.1(b) mouse share many characteristics with their B6 counterparts, but seem to be deficient in the functional NKT cell subtype characterized by low interleukin-4 and high interferon-gamma production, and surface expression of CD49b but not CD69. Moreover, in the thymus but not the spleen of BALB.B6-NK1.1(b) mice we find a novel Valpha14-Jalpha18 invariant NKT cell subset which is devoid of a set of NK markers, suggesting that these cells represent a less differentiated NKT cell stage, and carries high levels of the T-cell receptor and uses a skewed T-cell receptor Vbeta-repertoire.     

Differential role of NK cells against Candida albicans infection in immunocompetent or immunocompromised mice

Little is known regarding the role of NK cells during primary and secondary disseminated Candida albicans infection. We assessed the role of NK cells for host defense against candidiasis in immunocompetent, as well as immunodeficient, hosts. Surprisingly, depletion of NK cells in immunocompetent WT mice did not increase susceptibility to systemic candidiasis, suggesting that NK cells are redundant for antifungal defense in otherwise immunocompetent hosts. NK‐cell‐depleted mice were found to be protected as a consequence of attenuation of systemic inflammation. In contrast, the absence of NK cells in T/B/NK‐cell‐deficient NSG (NOD SCID gamma) mice led to an increased susceptibility to both primary and secondary systemic C. albicans infections compared with T/B‐cell‐deficient SCID mice. In conclusion, this study demonstrates that NK cells are an essential and nonredundant component of anti‐C. albicans host defense in immunosuppressed hosts with defective T/B‐lymphocyte immunity, while contributing to hyperinflammation in immunocompetent hosts. The discovery of the importance of NK cells in hosts with severe defects of adaptive immunity might have important consequences for the design of adjunctive immunotherapeutic approaches in systemic C. albicans infections targeting NK‐cell function.     

Fine tuning of natural killer cell specificity and maintenance of self tolerance in MHC class I-deficient mice

TAP1 −/−, β2-microglobulin (β2m) −/− and TAP1/β2m −/− mice all express low but quantitatively different levels of MHC class I molecules. Using these mice, we have addressed questions relating to the fine tuning of natural killer (NK) cell specificity and maintenance of self tolerance in the NK cell system. NK cells from B6 wild-type mice killed target cells from TAP1 −/−, β2m −/− and TAP1/β2m −/− mice in vivo and rejected bone marrow grafts from the same mice in vivo at equivalent levels. NK cells from TAP1 −/−, β2m −/− mice did not kill target cells or reject bone marrow grafts from TAP1/β2m −/− mice. NK cells in all MHC class I-deficient mice were tolerant to autologous MHC class I-deficient cells, as revealed by in vitro cytotoxicity assays using NK cell effectors activated with the interferon-inducing agent Tilorone, or by in vivo bone marrow graft experiments. However, the self-tolerant state of MHC class I-deficient NK cells was broken by in vitro stimulation with IL-2 for 4 days. Under these conditions, NK cells from the MHC class I-deficient mice killed autologous MHC class I-deficient cells while MHC class I-positive targets were spared. The C-type lectin inhibitory receptor Ly49C has a specificity for H-2K^b and is expressed on a subset of NK1.1⁺ cells in B6 mice. Wild-type and all MHC class I-deficient mice had similar numbers of Ly49C-positive NK1.1⁺ cells. However, Ly49C expression was markedly down-regulated on NK1.1⁺ cells from B6 mice, as compared to TAP1 −/−, β2m −/− and TAP1/β2m −/− mice. In vitro stimulation of NK cells with IL-2 for 4 days did not significantly change this pattern. The present results are discussed in relation to the role of MHC class I molecules and Ly49 receptors in shaping the NK cell repertoire and raise new questions about maintenance of self tolerance in the NK cell system.     

Hybrid Resistance to EL-4 Lymphoma Cells

(C57BL/6 × DBA/2)F₁ hybrid (B6D2F₁) mice resist the growth of parental-strain (B6) EL-4 lmphoma cells inoculated intraperitoneally; that is, B6D2F₁ mice survive longer than B6 mice and do not develop uscites As compared with B6 mice, B6D2F₁ mice have higher levels of natural killer (NK) activity against ⁵¹Cr-labelled EL-4 cells in their lyphiod organs. B6D2F₁ mice treated with ⁸⁹Sr lose NK activity for certain lymphoma cell targets, e.g. YAC-1, but NK(EL-4) function is usually intact. However, ⁸⁹Sr-treated mice had hybrid resistance to EL-4 cell in vivo, as determined by survival times and the development of ascites. NK(EL-4) and NK-(YAC-1) activities were stimulated by irrudiated or unirradiated EL-4 cells, Corynebacterium parvum, or polyinosinic:polycytidylic acid (pl:pC) in spleens of normal B6D2F₁ mice, but NK(EL-4) activity was depressed Within 3 days by such treatment in B6D2F₁ mice previously injected with ⁸⁹Sr. Suppressor cells for NK(EL-4) but not for NK(YAC-1) effectors were easily detected in spleens of ⁸⁹Sr-treated mice ‘challenged’ with C. parvum. Thus, agents capable of Stimulating NK cell function in normal mice may lead to suppression of that activity in mice depleted of marrow-dependent cell function by ⁸⁹Sr. Spleen cells of ⁸⁹Sr-treated B6D2F₁ mice were also unable to generate anti-EL-4 cytotoxic T lymphocytes in a cell-mediated lympholysis system; this defect appeared also in to be mediated by suppressor cells. Lymphoid cell depleted by ⁸⁹Sr-induced marrow aplasia may have two functions in host defences against tumours (especially lymphomas): they may lyse tumour cells directly and they may ‘down-regulate’ suppressor cells capable of inhibiting other ‘natural’ or ‘induced’ immune functions.     

A lupus-susceptibility C57BL/6 locus on chromosome 3 (Sle18) contributes to autoantibody production in 129 mice

Epistatic interactions between the non-autoimmune strains 129 and C57BL/6 (B6), used for generating gene-targeted animals, can induce a lupus-like disease. Genome-wide scan analyses of testcross progeny between these two strains have identified several lupus susceptibility loci, with the strongest linkage to the production of autoantibodies (auto-Abs) displayed by an interval on chromosome 1 of 129 origin (Sle16). However, the contribution of B6 loci to the lupus phenotype remained unknown. We used a congenic approach to deduce the contribution to the autoimmune traits of the B6 genomic interval on chromosome 3 (Sle18), previously shown to be linked to antinuclear Ab production. This interval, when transferred on a 129 background (a strain termed 129.B6-Sle18), promoted auto-Ab production targeting a broad spectrum of autoantigens, expansion of activated CD4(+)T and B cells and mild glomerulonephritis. Surprisingly, these immunological and serological defects were accompanied by a significant increase in the percentage of regulatory T cells (Tregs; CD4(+) Foxp3(+)). However, these cells, that expressed lower levels of Foxp3, had no impaired regulatory function when tested in vitro. These findings illustrate further the efficacy of congenic dissection for functional characterisation of individual lupus susceptibility loci and highlight the contribution of loci derived from non-autoimmune strains to the disease pathogenesis.     

In vitro evidence from anti-hapten antibody responses for T helper and suppressor cells directed against major histocompatibility antigens in the mouse. Participation of I region determinants in the induction of T helper cells.

The antibody response to murine alloantigens is thought to be thymus-dependent. In this study, we were using H-2 and H-minor antigens presented on the surface of cells as particulate carriers and 2, 4, 6-trinitrophenyl (TNP) as a hapten. To study conditions for the induction of T helper and T suppressor cells directed against such antigens, T cell donor mice of a given inbred strain were primed with spleen cells of another inbred strain differing in distinct subregions of its H-2 haplotype and/or differing in its H-minor haplotype. Spleen T cells of mice in vivo allogeneically (carrier)-primed in this way were cocultured in vitro with splenic in vivo TNP (hapten)-primed B cells plus irradiated TNP-conjugated spleen cells (hapten-carrier conjugate) from the haplotype used for carrier priming. The anti-hapten antibody response was taken as a quantitative indicator of helper activity. Suppression was tested by measuring the reduction of the antibody-forming cell response of in vivo TNP or sheep red blood cell (SRBC)-primed B cells restimulated in vitro with homologous antigen in the presence of allogeneically primed T cells. Helper cell functions were clearly demonstrated when donors of T cells were primed to Ia antigens. Additional priming to K and/or D antigens yielded help and suppres- sion simultaneously, priming to K and/or D antigens alone and in some cases to H- minor antigens yielded no help but resulted in strong suppression. The effect of the helper cells was shown to be camer-specific occurring only in the presence of the relevant carrier, whereas the suppressor T cells were of the nonspecific type sup- pressing both anti-TNP and anti-SRBC responses in the absence of any restimulating carrier. The helper effect was seen not only when the hapten was conjugated to the appropriate (allogeneic) cells but also when it was presented on an unrelated carrier (syngeneic cells) provided that the specific nonhaptenated carrier was present. - Pos- sible recognition mechanisms are discussed.     

The in vitro production of anti-nuclear antibodies by human peripheral blood mononuclear cells. Demonstration of T cell requirement and soluble inducing factor(s) for anti-nuclear antibodies triggering in patients with systemic lupus erythematosus.

Peripheral blood mononuclear cells (PBMC) of 29 patients with systemic lupus erythematosus (SLE) and 14 normal individuals were investigated for the in vitro production of anti-nuclear antibodies (ANA). Twenty-eight of 29 SLE patients but only one control spontaneously produced ANA in unstimulated PBMC. Pokeweed mitogen induced ANA synthesis in six controls. No detectable ANA was observed in B cell enriched fraction except in two cases of SLE. Recombination of B + T cell enriched fractions and PBMC supernatants from SLE patients could induce B cells to synthesize ANA. These results indicate that: (1) SLE patients spontaneously produced ANA in vitro whereas controls rarely did; (2) autoreactive clones exist in normal individuals but are kept under control and (3) T cell help is required for ANA triggering.