Enhanced response of autoantibody-secreting B cells from young NZB/NZW mice to T-cell-derived differentiation signals

The effect of prolactin on immune cell subsets involved in SLE pathogenesis

The higher frequency of autoimmune diseases in the female population compared to males suggests that certain hormones, such as prolactin (PRL), play a role in determining the prevalence of autoimmunity in women, particularly during childbearing age. PRL can act not only as a hormone but also as a cytokine, being able to modulate immune responses. Hyperprolactinemia has been implicated in the pathogenesis of various autoimmune diseases where it may affect disease activity. One of the conditions where PRL has such a role is systemic lupus erythematosus (SLE). PRL regulates the proliferation and survival of both lymphoid and myeloid cells. It also affects the selection of T-cell repertoires by influencing the thymic microenvironment. In autoimmune conditions, PRL interferes with the activity of regulatory T cells. It also influences B cell tolerance by lowering the activation threshold of anergic B cells. The production of CD40L and cytokines, such as interleukin IL-6, are also promoted by PRL. This, in turn, leads to the production of autoantibodies, one of the hallmarks of SLE. PRL increases the cytotoxic activity of T lymphocytes and the secretion of proinflammatory cytokines. The production of proinflammatory cytokines, particularly those belonging to the type 1 interferon (IFN) family, is part of the SLE characteristic genetic signature. PRL also participates in the maturation and differentiation of dendritic cells, promoting the presentation of autoantigens and high IFNα secretion. It also affects neutrophil function and the production of neutrophil traps. Macrophages and dendritic cells can also be affected by PRL, linking this molecule to the abnormal behavior of both innate and adaptive immune responses.This review aimed to highlight the importance of PRL and its actions on the cells of innate and adaptive immune responses. Additionally, by elucidating the role of PRL in SLE etiopathogenesis, this work will contribute to a better understanding of the factors involved in SLE development and regulation.

Immunoglobulin deficient mice generated by gene targeting as models for studying the immune response

B cell deficient animals obtained by various strategies of gene targeting were used to study the B cell development and examine the role of different immune compartments in the immune response to microbes. Study of muMT, JHD, lambda 5T and JHT models of B cell deficiency, was essential in order to understand the role of pre-B cell receptor in B cell development, allelic exclusion and variable gene rearrangement regulation. In the immune response to influenza virus, a protective role of T cells in a total absence of B cell compartment, was revealed by studying the JHD -/- model. Further, it was established that a T cell compartment is sufficient to mediate the recovery from influenza infection. Examination of immune response in muMT and JHD models of definitive B cell deficiency to various blood stage Plasmodia species, showed that whereas B cells are not required for recovery from infection with P. chabaudi adami, P. vinckei petteri and P. chabaudi chabaudi (CB), B cell compartment is important in the later stages of infection with P. chabaudi chabaudi (AS). Studies carried out in muMT model suggested a possible role for T gamma delta subpopulation in the immune response to blood stage malaria parasite. B cell deficiency models are valuable for understanding the normal and pathological immune response. Studies carried out in muMT model indicated that T cell responses are not significantly affected in the absence of B cells. These data can neither rule out a role for B cells in T cell priming, nor in triggering an effective T cell help for humoral response. Study of double homozygous mice deficient for B cells and FAS or IL-2 gene, pinpointed the role of B cells in pathogenesis of lupus-like nephritis and vasculitis from lpr mouse and in hemolytic anemia from IL-2 -/- mouse model, respectively.

The role of B cells in lpr/lpr-induced autoimmunity

The primary roles of T cells and B cells in the initiation of systemic autoimmunity are unclear. To investigate the role of B cells, we crossed the "Jh knockout" mutation onto the autoimmune lpr/lpr background. Animals homozygous for both traits were obtained. As expected, these animals lack B cells. These animals also show no signs of autoimmune kidney destruction nor vasculitis, in spite of carrying the lpr/lpr mutation. In contrast, lpr/lpr littermates that had B cells had severe nephritis and vasculitis, as well as autoantibodies. These results demonstrate a primary role for B cells and/or (auto)antibodies in initiating several types of autoimmune-mediated tissue destruction. The implications of this finding for models and therapy of autoimmunity are discussed.

Interleukin 6 promotes murine lupus in NZB/NZW F1 mice

To investigate the role of IL-6 in systemic lupus erythematosus (SLE), we selectively inhibited IL-6 in lupus-prone NZB/NZW F1(B/W) mice by chronic administration of a rat mAb to mouse IL-6. Anti-IL-6 alone elicited an anti-rat response that blocked its biologic effects. To circumvent this problem, we rendered B/W mice tolerant to the rat mAb by administration of anti-CD4 concurrent with the first dose of anti-IL-6. Thereafter, the mice received weekly injections of anti-IL-6 alone. There were two control groups: one group received the tolerizing regimen of anti-CD4 along with a control rat IgG1 mAb (GL113) instead of anti-IL-6; the other control group received PBS. Mice that received anti-CD4 were tolerant to the rat mAb for 6 mo. Throughout this period, treatment with anti-IL-6 prevented production of anti-dsDNA, significantly reduced proteinuria, and prolonged life. Mice that received anti-IL-6 without anti-CD4 developed an immune response to the rat mAb and then developed anti-dsDNA antibodies, proteinuria, and mortality comparable with control mice. These findings establish that IL-6 promotes autoimmunity in B/W mice. They further indicate that, although mAb to IL-6 can suppress murine lupus, the development of host immunity to the mAb abrogates its beneficial effects. Finally, this is the first study to demonstrate that a brief course of anti-CD4 can induce tolerance to another therapeutic mAb, in this case an anti-cytokine mAb.

Functional role of self IA molecules in polyclonal B cell activation using an autoreactive B cell clone derived from (NZB X NZW) F1 mice

The mechanism of polyclonal B cell activation in autoimmune diseases was investigated by using an autoreactive B cell clone established by somatic hybridization with B cells derived from NZB X NZW (B/W) F1 mice. Briefly, splenic B cells from B/W F1 mice were fused with M12.4.1, a mutant of a B cell line, in the presence of polyethylene glycol and DMSO. NW47.7, a subclone of a resulting hybridoma, expresses B cell surface antigens on the cell membrane, namely IAd, IgM, B220, the receptors for the C3 fragment of complement (C3R), and the Fc portion of IgG (Fc gamma R). It also possesses a receptor molecule for mouse red blood cells treated with bromelain (Br-MRBC) on its surface, by rosette-forming assay with Br-MRBC. In contrast, parental M12.4.1 does not express IAd and IgM on the cell membrane, and does not bind to Br-MRBC under the same conditions. Thus, it is likely that NW47.7 may be an autoreactive B cell clone specific for Br-MRBC. Interestingly, NW47.7 was induced to generate a significant number of IgM-secreting cells when treated with Br-MRBC and rIL-5. Furthermore, mAb against IAd molecules, but not IAk and KdDd, markedly inhibited the differentiative effect of polyclonal activators such as LPS and rIL-5. Also, when MHC identical irradiated B cells were added to the culture of NW47.7 as a stimulator, the induction of IgM-producing cells was greatly augmented, but this augmenting effect was lost by interfering with direct contact of NW47.7 cells with stimulator B cells using a semipermeable membrane, as well as by the addition of mAb against IAd molecules. In addition, irradiated NW47.7, but not M12.4.1, by itself could enhance the secretion of IgM by NW47.7 as a stimulator, but this enhancing effect markedly decreased in the presence of anti-IAd mAb. The present results suggest that surface IA molecules on B cells are involved during the differentiative response to polyclonal activators, and may directly provide a differentiative signal for maturation of B cells into IgM-secreting cells.

Rheumatoid factor and Fc signaling: a tale of two Cinderellas

Signaling to lymphocytes depends not only upon the interaction of receptors with specific antigen, but also upon antigen nonspecific receptors which receive input from two classes of molecules, immunologically specific end products and lymphokines. These represent the central elements in the physiologic stimulation of immune responses to both self and foreign antigens. This review is dedicated primarily to describing the function of physiologically active receptors for end product which are central to end product feedback in normal immune responses. The emergence of autoimmunity as a pathologic process resultant from a defective end product signaling mechanism is described.

Deletion of potentially self-reactive T cell receptor specificities in L3T4-, Lyt-2- T cells of lpr mice

The current study examines the possibility that the TCR repertoire of L3T4-, Lyt-2- cells in lpr/lpr mice is enriched for self-reactive specificities. T cells utilizing V beta 17a and V beta 8.1 gene products have been shown to be clonally eliminated in nonautoimmune mice expressing I-Ek and Mlsa/H-2k, respectively, because of their potential self reactivity. We quantitated these V beta specificities in lymph nodes and spleens of lpr/lpr mice. The results indicate that lpr-dependent L3T4-/Lyt-2- T cells, similar to normal peripheral T cells, have undergone a repertoire modification such that potential self-reactive V beta specificities have been eliminated. Evidence for tolerance in this population provides insight into the development of these aberrant cells, and may also have important implications for normal T cell development in the thymus.

Lupus nephropathy in New Zealand F1 hybrid mice treated by (-)15-deoxyspergualin

The effect of (-)15-deoxyspergualin (15-dsp), a new immunosuppressant which was originally separated from the culture filtrate of a strain of Bacillus laterosporus, was evaluated in this study. Various doses of 15-dsp were subcutaneously administered to New Zealand black/white F1 hybrid mice (B/WF1) four times a week starting at 14 weeks of age, just prior to the onset of nephropathy. The life span of the treated animals, studied at 0.6 to 6.0 mg/kg body weights, compared with the control mice was significantly prolonged by 15-dsp treatment (percent survival of the treated mice at 50 to 70 weeks of age was significantly higher than that of the control mice, except that of the 0.6 mg group at 60 wks of age, P less than 0.05 by Fisher's exact test). In the 6.0 mg group of mice, complete suppression of spontaneously progressive splenomegaly with decreased total spleen cells was observed at 24 through 36 weeks of age compared with the same-aged control group of mice (P less than 0.01). Absolute numbers of L3T4+ splenocytes determined by flow cytometry, as well as L3T4+/Lyt2+ ratio, were decreased, while in vitro interleukin 2 production by splenocytes induced with staphylococcal enterotoxin A was significantly enhanced. Serum IgG anti-ds DNA antibody levels, measured by radioimmunoassay in the treated mice, were significantly lower at 24 through 36 weeks of age than those in the control mice (P less than 0.01), and the incidence of significant proteinuria (greater than or equal to 100 mg/dl) in the 15-dsp group was lower at both 32 and 36 weeks of age (P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

In vitro anti-histone antibody production by peripheral blood cells from patients with systemic lupus erythematosus

Anti-histone antibodies (AHA) have been demonstrated frequently in the sera of patients with systemic lupus erythematosus (SLE). In the present studies, we found that peripheral blood mononuclear leukocytes (PBL) from a large subset of SLE patients spontaneously produce elevated levels of AHA in culture. In contrast, detectable production by normal mononuclear cells was extremely rare. Spontaneous production by patients' PBL correlated with both disease activity and elevated serum AHA levels, and thus appeared to reflect in vivo production. Interestingly, spontaneous AHA production was independent of polyclonal B-cell activation as measured by total Ig synthesis in culture. Production also appeared to be T-cell-independent in that cultures depleted of T cells produced AHA levels similar to those of cultures with unseparated PBL. Although PBL from normal individuals rarely produce AHA spontaneously, the presence of histone-specific B cells in normal peripheral blood could be detected after pokeweed mitogen stimulation. The present studies provide a basis for a further understanding of the mechanisms responsible for autoantibody production in SLE.