Multivariate one-sided testing in matched observational studies as an adversarial game

We present a multivariate one-sided sensitivity analysis for matched observational studies, appropriate when the researcher has specified that a given causal mechanism should manifest itself in effects on multiple outcome variables in a known direction. The test statistic can be thought of as the solution to an adversarial game, where the researcher determines the best linear combination of test statistics to combat nature’s presentation of the worst-case pattern of hidden bias. The corresponding optimization problem is convex, and can be solved efficiently even for reasonably sized observational studies. Asymptotically, the test statistic converges to a chi-bar-squared distribution under the null, a common distribution in order-restricted statistical inference. The test attains the largest possible design sensitivity over a class of coherent test statistics, and facilitates one-sided sensitivity analyses for individual outcome variables while maintaining familywise error control through its incorporation into closed testing procedures.

Delayed bowel erosion by tension-free vaginal tape (TVT)

A 71-year-old woman who had had a previous abdominal hysterectomy and Burch operation presented with stress urinary incontinence due to intrinsic urethral sphincter deficiency. She underwent a technically difficult placement of a TVT tape in April 2002. After an uneventful recovery she was discharged after 72 hours but presented almost 5 months later with small bowel obstruction. At laparotomy she had a loop of ileum adherent to the left lower side wall of the pelvis, with the TVT tape penetrating and traversing this loop. The ileal segment was excised and an end-to-end anastomosis performed. Her recovery was uneventful and she is maintaining her urinary continence. Patients who have had previous combined pelvic intra- and extraperitoneal surgery should be operated on by experienced surgeons and be observed for 24 hours. The placement of a Uratape (Porges-Mentor) via a transobturator approach should also be considered in such cases.

Differences by race, sex and age in the clinical and immunologic features of recently diagnosed systemic lupus erythematosus patients in the southeastern United States

We examined the prevalence of clinical and immunologic features of systemic lupus erythematosus (SLE) by race, sex and age in a population-based study of 265 SLE patients. Patients fulfilled the American College of Rheumatology classification criteria. The median time between diagnosis and study enrollment was 13 months. The clinical and hematologic data were limited to occurrences up to 6 months after the diagnosis date, as documented in medical records. We used sera collected at study enrollment from 244 (92%) patients for serologic testing of autoantibodies. The associations between clinical and immunological features of SLE and age, sex and race were examined using logistic regression. The effect of each of these variables was examined adjusting for the other two demographic factors. Mean age at diagnosis was 6 years younger among African-Americans and other minorities compared with white patients (P < 0.01). Discoid lupus, proteinuria, anti-Sm and anti-RNP autoantibodies were more commonly seen in African-American patients, with odds ratios higher than 3.0. Photosensitivity and mucosal ulcers were noted less often in African-American patients. Proteinuria, leukopenia, lymphopenia and thrombocytopenia were approximately three times more common in men compared with women. The prevalence of oral or nasal ulcers and anti-DNA autoantibodies declined with age. The extent to which the differences we observed reflect genetic or environmental influences on the disease process should be investigated.

Fas, ceramide and serum withdrawal induce apoptosis via a common pathway in a type II Jurkat cell line

Ceramide is a key mediator of apoptosis, yet its role in Fas-mediated apoptosis is controversial. Some reports have indicated that ceramide is either a primary signaling molecule in Fas-induced cell death, or that it functions upstream of Fas by increasing FasL expression. Other studies have suggested that ceramide is not relevant to Fas-induced cell death. We have approached this problem by studying ceramide-induced apoptosis in unique Jurkat cell clones selected for resistance to membrane-bound FasL-induced death. Resistance of the mutant Jurkat cells was specific for FasL killing, since the mutant clones were sensitive to other apoptotic stimuli such as cycloheximide and staurosporine. We tested the effects of serum withdrawal, one of the strongest inducers of ceramide, and of exogenous ceramide on apoptosis of both wild-type and FasL-resistant clones. Wild-type Jurkat cells were remarkably sensitive to serum withdrawal and to exogenous ceramide. In contrast all FasL-resistant mutant clones were resistant to these apoptosis-inducing conditions. In contrast to previous work, we did not detect an increase in FasL in either wild-type or mutant clones. Moreover activation of stress-activated protein kinases (JNK/SAPKs) after serum withdrawal and exogenous ceramide treatment was detected only in the wild-type and not in the resistant clones. Because of the parallel resistance of the mutant clones to Fas and to ceramide-induced apoptosis, our data support the notion that ceramide is a second messenger for the Fas/FasL pathway and that serum withdrawal, through production of ceramide, shares a common step with the Fas-mediated apoptotic pathway. Finally, our data suggest that activation of JNK/SAPKs is a common mediator of the three pathways tested.

The one-piece orbitozygomatic approach: the MacCarty burr hole and the inferior orbital fissure as keys to technique and application

OBJECTIVE

Use of the MacCarty keyhole burr hole and the inferior orbital fissure provides simplicity and safety to perform the one-piece frontotemporal orbitozygomatic (FTOZ1) approach.

METHODS

We performed the FTOZ1 approach with its three subtypes (i.e., total, temporal, and frontal) in cadaveric head specimens in the Goodyear Laboratory and subsequently in surgical cases.

RESULTS

The orbitozygomatic osteotomy, when added to a frontotemporal craniotomy, comprises the frontotemporal orbitozygomatic (FTOZ) approach, provides an expanded exposure to the anterior and middle cranial fossae, and enables the surgeon to create a window to the posterior cranial fossa. The MacCarty burr hole is used to facilitate orbital cuts, and the anterolateral portion of the inferior orbital fissure connects the orbital cuts to the zygomatic cuts. This allows the FTOZ1 craniotomy flap to be "out-fractured" with ease. The three types of FTOZ1 approach, i.e., the total, the temporal, and the frontal, are described step by step.

CONCLUSIONS

Understanding the MacCarty keyhole burr hole and the microsurgical anatomy of the inferior orbital fissure is essential to performing the FTOZ1 approach. The three types of FTOZ1 approach enable the surgeon to tailor the approach according to the surgical exposure needed for each lesion.

Early carotid endarterectomy for critical carotid artery stenosis after thrombolysis therapy in acute ischemic stroke in the middle cerebral artery

BACKGROUND AND PURPOSE

Tissue plasminogen activator (tPA) has been shown to be effective for acute ischemic stroke. However, if a high-grade cervical carotid stenosis remains despite tPA therapy, patients are at risk for recurrent stroke. Carotid endarterectomy (CEA) has been shown to be effective in symptomatic patients with high-grade cervical carotid stenosis in reducing the risk of stroke, but it is unknown whether CEA can be performed safely after tPA thrombolysis. We describe our experience with 5 patients who underwent early (<48 hours) CEA for residual high-grade cervical carotid stenosis after thrombolytic therapy for acute ischemic stroke in the middle cerebral artery territory.

METHODS

All patients had a critical (>99%) carotid artery stenosis on the symptomatic side after tPA therapy. All patients received intravenous tPA; 3 patients also received intra-aortic tPA. Three patients received intravenous heparin infusion immediately after administration of tPA. All patients showed marked improvement in their National Institutes for Health Stroke Scale scores after treatment with tPA. CEA was then performed within 45 hours (6 hours in 1 patient, 23 hours in 2, 26 hours in 1, and 45 hours in 1).

RESULTS

All 5 patients underwent successful CEA. There were no complications related to surgery. At discharge, 2 patients had a normal examination, and the remaining patients had mild deficits. In a long-term follow-up of 5 to 22 months, no patient had a recurrent cerebrovascular event.

CONCLUSIONS

Early CEA can be performed safely and successfully in patients after tPA treatment for acute ischemic stroke in appropriately selected patients.

Phagocytosis and clearance of apoptotic cells is mediated by MER

Apoptosis is fundamental to the development and maintenance of animal tissues and the immune system. Rapid clearance of apoptotic cells by macrophages is important to inhibit inflammation and autoimmune responses against intracellular antigens. Here we report a new function for Mer, a member of the Axl/Mer/Tyro3 receptor tyrosine kinase family. mer(kd) mice with a cytoplasmic truncation of Mer had macrophages deficient in the clearance of apoptotic thymocytes. This was corrected in chimaeric mice reconstituted with bone marrow from wild-type animals. Primary macrophages isolated from mer(kd) mice showed that the phagocytic deficiency was restricted to apoptotic cells and was independent of Fc receptor-mediated phagocytosis or ingestion of other particles. The inability to clear apoptotic cells adequately may be linked to an increased number of nuclear autoantibodies in mer(kd) mice. Thus, the Mer receptor tyrosine kinase seems to be critical for the engulfment and efficient clearance of apoptotic cells. This has implications for inflammation and autoimmune diseases such as systemic lupus erythematosus.

B and T cell responses to the spliceosomal heterogeneous nuclear ribonucleoproteins A2 and B1 in normal and lupus mice

Autoantibodies directed against spliceosomal heterogeneous nuclear ribonucleoproteins (hnRNPs) are a typical feature of rheumatoid arthritis, systemic lupus erythematosus, and mixed-connective tissue disease. With the aim of investigating a potential pathogenic role of these Abs, we have studied the Ab response to A2/B1 hnRNPs in different murine models of lupus. The specificity of anti-A2/B1 Abs was tested with a series of 14 overlapping synthetic peptides covering the region 1-206 of A2 that contains most of the epitopes recognized by patients' Abs. A major epitope recognized very early during the course of the disease by Abs from most of MRL lpr/lpr mice but not from other lupus mice and from mice of different MHC haplotypes immunized against B1 was identified in residues 50-70. This peptide contains a highly conserved sequence RGFGFVTF also present in other hnRNPs and small nuclear ribonucleoproteins. Abs reacting with a second A2 epitope identified in residues 35-55 were detectable several weeks later, suggesting an intramolecular B cell epitope spreading during the course of the disease. We identified several T cell epitopes within the region 35-175 that generated an effective Th cell response with IL-2 and IFN-gamma secretion in nonautoimmune CBA/J mice sharing the same MHC haplotype H-2k as MRL/lpr mice. None of the peptides stimulated T cells primed in vivo with B1. Because Abs to peptide 50-70 were detected significantly earlier than Abs reacting with other A2 peptides and the protein itself, it is possible that within the protein, this segment contains residues playing an initiator role in the induction of the anti-A2/B1 and antispliceosome Ab response.

MHC class II-bound self peptides from autoimmune MRL/lpr mice reveal potential T cell epitopes for autoantibody production in murine systemic lupus erythematosus

The systemic lupus erythematosus-like syndrome in MRL/lpr mice involves high-titered IgG autoantibodies, particularly antinuclear Abs that target histones, DNA, and RNA particles. Although T cell help is required for the generation of antinuclear Abs, the epitopes recognized by such helper T cells are unknown. To address this question, we isolated and sequenced self peptides bound by MHC class II molecules from MRL/lpr mice. We identified a number of peptides that are not seen in similar preparations from nonautoimmune C3H animals. The "abnormal" peptide donors include histone, a protein component of a small nuclear ribonucleoprotein, ribosomal proteins, and RNA processing enzymes. We postulate that the peptides from these donors are T cell epitopes required for the generation of the most frequent antinuclear Abs specificities seen in MRL/lpr mice.

Spontaneous and induced apoptosis in systemic lupus erythematosus: multiple assays fail to reveal consistent abnormalities

The immunologic basis of systemic lupus erythematosus (SLE) is multifactorial and still elusive. Recent advances in the field of apoptosis have suggested new paradigms for the development of lupus autoimmunity. In the present studies we examined the possibility that individual populations of T and B cells are abnormally resistant to apoptosis or that they stand out in over- or underexpressing Fas. Fas was generally overexpressed in cells freshly isolated from SLE patients but the apoptotic response to FasL was normal. We did not find increased spontaneous ongoing apoptosis in SLE lymphocytes. Normal cleavage of PARP similarly implied that the final biochemical pathway of apoptosis is relatively intact in SLE. Finally we placed special emphasis on the response of SLE patient cells to UV irradiation, especially cells from photosensitive patients, and found no difference in Fas expression. In conclusion our results indicate that SLE patients do not suffer from a major apoptotic abnormality. The results also raise questions concerning the dynamic expression of Fas and the significance of ongoing apoptosis as a risk for autoimmune disease.

Apoptosis provoked by the oxidative stress inducer menadione (Vitamin K(3)) is mediated by the Fas/Fas ligand system

Menadione, or vitamin K(3) (VK(3)), a potent oxidative stress inducer, has been recently used as an effective and remarkably safe cytotoxic drug for treatment of several human tumors. VK(3) induces apoptotic cell death through a poorly understood mechanism. Here we show for the first time that VK(3)-induced apoptosis requires the Fas/FasL system. Spleen cells from both Fas- and FasL-deficient mice (C57BL/6-lpr and C57BL/6-gld, respectively) had much lower levels of VK(3) apoptosis in vitro compared to cells from control C57BL/6 mice. VK(3) cytotoxicity toward mouse splenocytes was also blocked with a Fas-Fc fusion protein. VK(3) induced apoptosis in Jurkat cells, coincident with an increase in both Fas and FasL expression. A FasL-resistant variant of these Jurkat cells was also resistant to VK(3)-induced apoptosis. Furthermore, because VK(3) effects were inhibited by glutathione, a potent antioxidant, oxidative stress was linked to the Fas/FasL system. Moreover, since the Jurkat cell lines were p53 null, the activation of Fas/FasL system after oxidative stress apparently acted through a p53-independent pathway. The therapeutic relevance of the K vitamins has been growing in recent years; our findings offer new insight for improving and expanding their applications.

Differential control of autoantibodies and lymphoproliferation by Fas ligand expression on CD4+ and CD8+ T cells in vivo

We have previously shown that the gld autoimmune syndrome is suppressed in lethally irradiated gld mice reconstituted with a mixture of normal and gld bone marrow (BM). Furthermore, in vivo depletion of normal Thy-1+ cells restores lymphoproliferation and autoantibody production in such chimeras, suggesting that T cells bearing Fas ligand are responsible for correcting the gld defect. In this study, mixed-BM chimeras lacking either normal CD4+ (B6CD4KO-B6gld) or normal CD8+ T cells (B6CD8KO-B6gld) were generated to determine the contribution of the normal T cell subsets to disease suppression. Lymphoproliferation was completely suppressed in B6CD4KO-B6gld chimeras but only modestly in B6CD8KO-B6gld chimeras. On the other hand, both types of mixed-BM chimeras had incomplete effects on the suppression of serum autoantibodies when compared with B6gld reconstituted with isologous BM. These results suggest that both T cell subsets provide Fas ligand to suppress immune cells responsible for autoantibody production; however, CD8+ T cells are mainly responsible for preventing lymphoproliferation.

The role of environmental antigens in the spontaneous development of autoimmunity in MRL-lpr mice

It has been proposed that the "normal" stimulation of the immune system that occurs from interactions with environmental stimuli, whether infectious or dietary, is necessary for the initiation and/or continuation of autoimmunity. We tested this hypothesis by deriving a group of MRL-lpr mice into a germfree (GF) environment. At 5 mo of age, no differences between GF and conventional MRL-lpr mice were noted in lymphoproliferation, flow cytometric analysis of lymph node cells (LN), or histologic analysis of the kidneys. Autoantibody levels were comparably elevated in both groups. A second experiment tested the role of residual environmental stimuli by contrasting GF mice fed either a low m.w., ultrafiltered Ag-free (GF-AF) diet or an autoclaved natural ingredient diet (GF-NI). At 4 mo of age, both groups showed extensive lymphoproliferation and aberrant T cell formation, although the GF-AF mice had approximately 50% smaller LNs compared with sex-matched GF-NI controls. Autoantibody formation was present in both groups. Histologic analysis of the kidneys revealed that GF-AF mice had much lower levels of nephritis, while immunofluorescence analysis demonstrated no difference in Ig deposits but did reveal a paucity of C3 deposition in the kidneys of GF-AF mice. These data do not support a role for infectious agents in the induction of lymphoproliferation and B cell autoimmunity in MRL-lpr mice. Furthermore, they suggest that autoantibodies do not originate from B cells that were initially committed to exogenous Ags. They do suggest a possible contributory role for dietary exposure in the extent of lymphoproliferation and development of nephritis in this strain.

Ectopic expression of B7-1 (CD80) on T lymphocytes in autoimmune lpr and gld mice

Defective Fas-mediated apoptosis in mice, caused by the gld mutation in the fas ligand gene, results in the development of lupus-like autoantibodies and severe lymphoproliferation. We previously demonstrated ectopic expression of the costimulatory molecule B7-1 (CD80) on T lymphocytes in B6/gld mice. This report extends these observations by demonstrating similar results in B6/lpr mice, which possess a mutation in the gene encoding Fas. Additionally, we demonstrate that this phenomenon is age-dependent and occurs on multiple subsets of B6/gld T lymphocytes. B7-1 upregulation is observed on T cells from both conventionally housed and specific-pathogen-free B6/gld mice, suggesting that this is not a consequence of infection by pathogen. T cells from lpr and gld mice show increased binding of CTLA4-Ig fusion protein, suggesting that the upregulated B7-1 is functional. CD28, a receptor for B7-1 which activates T cells, is upregulated in B6/lpr and B6/gld mice, while CTLA4, a negative regulator of T cells which binds B7-1, is not. Our results suggest that ectopic expression of B7-1 on T cells of lpr and gld mice may be playing a role in exacerbation of lymphoproliferation and/or autoimmunity.

Expression and function of Fas on cells damaged by gamma-irradiation in B6 and B6/lpr mice

Fas (CD95) is a cell surface protein that mediates apoptosis. lpr is a mutation of the Fas gene caused by a retroviral insertion resulting in premature termination of transcription and aberrant splicing of Fas mRNA. Mice homozygous for the lpr gene develop lymphoproliferation and produce autoantibodies closely resembling those of human systemic lupus erythematosus. While lpr mice have been reported to express low levels of normally spliced Fas mRNA, it is unknown whether they express functional Fas protein. Here we show that splenocytes from lpr mice that have been damaged by gamma-irradiation expressed Fas protein. Fas was up-regulated on irradiated B6 cells and could be detected on B6/lpr cells undergoing apoptosis following in vitro culture. Detection of Fas on live lpr cells was demonstrable when apoptosis was blocked by zinc. In a short term chimera system, Fas was shown to play a role, in vivo, in the disposition of radiation-injured cells from both normal and lpr mice. The addition of anti-Fas Ab to in vitro cultures resulted in an increase in apoptosis in both B6 and B6/lpr cells. Detection of intact Fas message and low levels of Fas protein in lpr mice has led to the consideration of lpr as a leaky mutation. This study demonstrates that lpr mice can produce functional Fas protein. This system is also appropriate for identifying the in vivo role of Fas/FasL in apoptosis following other cell manipulations.

Fas ligand (gld)- and Fas (lpr)-deficient mice do not show alterations in the extravasation or apoptosis of inflammatory neutrophils

Apoptosis of neutrophils plays a critical role in the resolution of acute inflammation. Neutrophils from human peripheral blood express Fas (CD95) and are sensitive to Fas ligand (FasL)/Fas-mediated apoptosis. Mice carrying spontaneous mutations in the genes for fas ligand (B6/gld) or fas (B6/lpr) were used to assess the role of FasL/Fas in the kinetics and magnitude of neutrophil extravasation to the thioglycolate (TG)-inflamed peritoneum and in the spontaneous apoptosis of TG-elicited neutrophils. The results showed that TG-elicited neutrophils (defined by flow cytometry as GR-1/Ly-6G(hi) cells) from normal (B6) and B6/gld mice, but not from the Fas-deficient B6/lpr mice, express high levels of Fas. The TG-elicited neutrophil response began at 2 h, peaked at 4 h, and subsided by 24-48 h after TG administration in all three strains. However, the response was more prolonged in B6 mice, such that B6/gld and B6/lpr mice had fewer neutrophils at 6 h after TG administration than did B6 mice. Further studies showed that 4 h TG-elicited neutrophils from B6, B6/gld and B6/lpr mice undergo apoptosis in vitro at similar rates (as assessed through flow cytometry by the decrease in forward angle light-scatter and externalization of phosphatidylserine (PS; as detected by Annexin V-FITC) that occur as neutrophils undergo apoptosis). Fas expression was down-regulated on apoptotic neutrophils in conjunction with maximal PS externalization and decreased forward angle light-scatter. Collectively, these findings suggest that FasL/Fas-mediated apoptosis is not essential in regulating the lifespan of neutrophils during an acute inflammatory response. The abbreviated inflammatory response observed in FasL/Fas-deficient mice is likely to be a secondary effect of the gld/lpr autoimmune/lymphoproliferative syndrome, and not a direct effect of FasL/Fas on the ability of inflammatory neutrophils to undergo apoptosis.

Mice deficient in fas ligand (gld) or fas (lpr) show few alterations in granulopoiesis

Evidence exists that the life span of mature, circulating neutrophils is influenced by apoptosis induced by interactions between Fas ligand (FasL) and Fas (CD95). However, the role of FasL/Fas-mediated apoptosis in granulopoiesis has not been explored. The present study assessed differences in granulopoiesis between normal (B6) mice and mice carrying mutations in the genes for FasL (B6/gld) or Fas (B6/lpr). Granulopoiesis was examined by quantitating mature granulocytes in the blood, committed myeloid progenitor cells (or colony-forming units; CFU) in the bone marrow (BM), and granulocyte lineage cells in the BM. The present study also characterized through flow cytometry the ability of GR-1(+) granulocyte lineage cells from B6, B6/gld, and B6/lpr mice to undergo spontaneous apoptosis in vitro. In comparison to B6 mice, B6/gld mice (but not B6/lpr mice) showed small, but significant increases in the number and percentage of blood granulocytes and in the number of myeloid CFU. However, the number and percentage of GR-1(+) granulocyte lineage cells in the BM were similar in the three strains. The rate of spontaneous apoptosis of GR-1(+) granulocyte lineage cells also did not differ between B6, B6/gld, and B6/lpr mice. In B6 and B6/gld mice, Fas expression on granulocyte lineage cells was downregulated in conjunction with a decrease in forward-angle light scatter (fsc) and externalization of phosphatidylserine (PS), two measures of apoptosis. These results suggest that FasL-Fas interactions play only a minor role in modulating numbers of committed myeloid progenitor cells and the size of the peripheral pool of mature granulocytes. Interactions between FasL and Fas do not influence the size of the BM pool of granulocyte lineage cells or the ability of those cells to undergo spontaneous apoptosis.

Anti-CD40L accelerates renal disease and adenopathy in MRL-lpr mice in parallel with decreased thymocyte apoptosis

The CD40/CD40L (CD40 ligand) axis regulates several interactions between T cells and B cells. Blocking of CD40 engagement by CD40L inhibits Ig class switch by B cells as well as diminishes T cell response to an immunizing Ag. For these reasons, disruption of CD40/CD40L interactions by anti-CD40L administration or by genetic disruption of CD40L has ameliorated a variety of autoimmune conditions. More recent findings suggest that a direct signal can be transmitted to T cells via their expressed CD40L, which can costimulate proliferation with CD3 or promote germinal center formation. It is therefore possible that treatment with anti-CD40L Ab might produce a different outcome than observed in genetically CD40L-deficient mice. In this regard, we observe that in contrast to the genetic deletion of CD40L in MRL-lpr mice, which diminishes autoimmune disease but has little effect on adenopathy, administration of anti-CD40L to MRL-lpr mice accelerates both of these parameters. This difference appears to result from anti-CD40L actively delivering a signal that inhibits T cell apoptosis in lpr mice. This was confirmed by in vitro studies demonstrating that CD40L cross-linking on lpr thymocytes inhibited apoptosis and surface TCR down-modulation induced by CD3 ligation.

Fas/Fas ligand interactions are involved in ultraviolet-B-induced human lymphocyte apoptosis

We wondered whether the apoptosis known to occur after UV-B irradiation might involve the Fas/Fas ligand (FasL) signaling pathway. We exposed PBLs from normal individuals, and also the Jurkat (E6-1) and U937 cell lines, to graded doses of UV-B irradiation and observed a prompt and marked increase in Fas expression at doses as low as 0.5 mJ/cm2. Increased Fas expression did not require new protein synthesis, since cycloheximide-treated cells also showed an increase in Fas after UV-B. UV-B-irradiated cells cultured in the presence of zinc showed inhibition of apoptosis coincident with a marked increase in Fas+ cells, apparently indicating the accumulation of Fas-bearing cells unable to undergo apoptosis. After UV-B irradiation, PBLs showed increased expression of Fas ligand; the E6-1 lymphocytic cell line also released soluble FasL. UV-B induced apoptosis could be partially blocked by neutralizing FasL Abs, and a FasL-resistant variant of E6-1 cell line showed reduced apoptosis after UV-B irradiation, implying that the increase in Fas expression signified a role for Fas in UV-induced apoptosis. UV-induced Fas expression may serve to target stress-injured cells for removal by FasL-bearing cells or by FasL produced by the cells themselves in response to the stimuli, and may represent a general function of the Fas/FasL pathway in facilitating the apoptosis and elimination of undesirable or harmful cells.

Immunological and pathological consequences of mutations in both Fas and Fas ligand

The lpr mutation in mice results in premature termination of transcription of the gene encoding the apoptosis-signaling receptor Fas. As a result, lpr mice develop severe lymphoproliferation and lupus-like autoantibodies. Growing evidence suggests that the lpr mutation is "leaky" and that low levels of Fas are expressed in lpr mice. To determine if Fas expressed in lpr mice is contributing to apoptosis we generated a novel strain of mice (B6/lprgld) which is homozygous for both the lpr mutation and the gld mutation which encodes nonfunctional Fas ligand (FasL) protein. If low levels of Fas in B6/lpr mice contribute to apoptosis and lessen the severity of disease, the B6/lprgld mice, which also lack functional FasL, would be expected to develop a more severe form of disease than B6/lpr mice. Our results revealed no significant increase in either lymphoproliferation or autoimmunity in B6/lprgld mice compared to B6/lpr or B6/gld mice. Additionally, no increase in surface expression of Fas was detected by flow cytometry on B6/lprgld lymphocytes compared to B6/lpr lymphocytes. However, histological examination of B6/lprgld liver revealed a marked increase in lymphocytic infiltration, compared to livers of B6/lpr and B6/gld mice. Our results suggest that, while low levels of Fas in lpr mice may not be contributing to amelioration of lymphoproliferation or autoimmunity, they may be partially protecting the liver from abnormalities which arise in the absence of Fas-mediated apoptosis.

Bone marrow and peripheral blood involvement in mantle cell lymphoma

The peripheral blood smears, bone marrow aspirates and biopsies of 46 patients with mantle cell lymphoma were reviewed. The diagnosis of mantle cell lymphoma was established in all cases on extramedullary tissue samples using standard morphologic, phenotypic and molecular genetic criteria. 27/35 patients (77%) had circulating lymphoma cells (median 200%m of all circulating white blood cells; range 5-90%) identified by morphology at some point during the course of their disease. No statistical difference in survival was detected in patients with or without peripheral blood involvement. Lymphoma was identified in bone marrow aspirate specimens from 33/40 patients (83%) and in bone marrow biopsy specimens from 39/43 patients (91%). The pattern of marrow biopsy involvement was nodular (31 cases; 82%), interstitial (19 cases; 50%), paratrabecular (17 cases, 45%) and diffuse (12 cases; 32%). Although the median survival of patients with > or = 50% bone marrow involvement was 13 months, and the median survival of patients with < or = 50% was 49 months; no statistically significant differences between these small subgroups were observed. Mantle cell lymphoma frequently involves the peripheral blood and bone marrow. Its appearance is distinctive but variable, and immunophenotypic studies as well as morphologic confirmation by a biopsy of tissue other than bone marrow is still required for diagnosis.

Novel immunoregulatory B cell pathways revealed by lpr-+ mixed chimeras

lpr, a murine mutation of the Fas apoptosis receptor, causes lymphadenopathy and autoantibody production, with lymphadenopathy primarily due to a population of CD4-CD8-B220+ T cells. Previous in vivo experiments, in which lpr and normal bone marrow cells were coinfused into lpr hosts, have demonstrated that only T cells of lpr origin accumulated abnormally and only B cells of lpr origin produced autoantibodies. Moreover, in these chimeras, B cells of normal origin were unable to respond to conventional, T cell-dependent exogenous Ag. To address the role of lpr B cells in regulation of lpr autoimmunity, we have prepared lpr-+ mixed chimeras and selectively eliminated lpr B cells using allele-specific, mAb treatment, thus allowing normal B cells to develop in an environment with lpr T cells. From these data, we arrived at four major conclusions: 1) Compared with control-treated chimeric mice, lpr B cell-depleted mice had greatly reduced total lymph node cell counts; 2) the T cells were derived equally from normal and lpr donors, and the percentage of lpr-derived CD4-CD8- T cells was greatly reduced; 3) despite the presence of the remaining lpr T cells, no autoantibodies were produced by the normal derived B cells; and 4) lpr T cells without lpr B cells were unable to prevent a normal B cell response to conventional Ag. These data demonstrate that B cells can play a critical and expansive regulatory role, not only for T cells, but for other B cells as well.

Acute myeloid leukemia with minimal differentiation. A multiple parameter study

Acute myeloid leukemia with minimal differentiation (AML-M0) is a recently described entity, and few large studies are available to characterize its clinical and pathologic features. We reviewed blood and bone marrow morphology, cytochemistry, immunophenotyping, and cytogenetics, as well as the clinical findings, of 17 patients with AML-M0. Most patients were male, with a median age of 62 years. Minimal background myelodysplastic features were identified in only 5 of 15 patients. Cytochemical stains for myeloperoxidase and alpha-naphthyl butyrate esterase were negative in the leukemic blasts of all specimens. Positivity for one or both myeloid-associated antigens, CD13 and CD33, was seen in all patients. Both CD34 and HLA-DR were positive in all tested cases. Lymphoid-associated antigens were identified in seven patients; these antigens were typically dim or weak in intensity. Terminal deoxynucleotidyltransferase positivity was seen in 14 of 14 tested patients; monoclonal anti-myeloperoxidase reactivity was seen in the blasts of 2 patients. Abnormal clonal karyotypes were found in 6 of 14 patients. Abnormalities of chromosomes 7 and 13 were the most common findings, most frequently manifested by monosomy 7 and trisomy 13. The median follow-up was 8 months. Eight patients died of their disease, three are alive with disease, and six are in first or second remission (including three patients treated with bone marrow transplantation). When narrowly defined, AML-M0 appears to be a homogeneous entity that affects older and predominantly male patients. It has no single karyotypic abnormality, but complex karyotypes with monosomy 7 and trisomy 13 are commonly found. Acute myeloid leukemia with minimal differentiation is relatively resistant to chemotherapy; however, bone marrow transplantation may provide a better outcome for eligible patients.

bca: an activation-related B-cell gene

We have identified a novel activation related B-cell gene (bca) through differential hybridization screening of a murine B cell cDNA library. The deduced amino acid sequence predicted a protein of 482 amino acids with strong sequence similarity to the SH2 and SH3 domains present within the non-catalytic regions of several protein tyrosine kinases. Northern analysis of RNA from several murine B-cell lines revealed a transcript of 1.8 kb, which was not detected in T-cell and non-lymphoid cell lines. bca was transcribed at low levels in resting spleen cells from a variety of normal mouse strains and was strongly expressed in kidney RNA. bca expression was markedly increased in RNA prepared from mitogen activated B cells, and in freshly isolated spleen and lymph node cells of MRL/lpr and NZB autoimmune strains. The unique sequence of bca, which bears no obvious similarity to any specific class of proteins containing SH2 and SH3 domains, suggests that this gene encodes a novel protein potentially involved in B-cell signal transduction.

Up-regulation of Fas and the costimulatory molecules B7-1 and B7-2 on peripheral lymphocytes in autoimmune B6/gld mice

C57BL/6-gld/gld (B6/gld) mice have a point mutation in the gene for Fas ligand (FasL) resulting in nonfunctional FasL protein. We hypothesized that the lack of normal Fas/FasL interactions in these mice might result in abnormalities of Fas expression. Thus, we compared spleen cells from B6/gld mice and normal B6 control mice. While B6 spleen cells consisted of two main populations, Fashigh (high Fas expression) and Faslow (low Fas expression), nearly all B6/gld spleen cells were Fashigh. Two-color immunofluorescence revealed that the Fashigh and Faslow populations in the B6 spleen were Thy-1.2+ (T cells) and IgM+ (B cells), respectively, whereas both T cells and B cells in the B6/gld spleen were Fashigh, indicating that Fas expression is increased on B cells in the B6/gld spleen. This phenomenon was age related and restricted to peripheral lymphocytes. In addition to Fas, B6/gld splenic B cells showed increased expression of the costimulatory molecule B7-2, while the related costimulatory molecule B7-1 was up-regulated on both B cells and T cells in the B6/gld spleen. In vitro, both B cells and T cells from the B6/gld spleen showed an increase in susceptibility to apoptosis mediated by soluble anti-Fas Ab. These results suggest that some lymphocytes in B6/gld mice are primed to undergo Fas-mediated apoptosis, but are unable to do so due to the absence of functional FasL. Further study of such abnormal lymphocytes in the B6/gld spleen may elucidate the nature of autoimmunity in these mice.

Up-regulation of Fas and the costimulatory molecules B7-1 and B7-2 on peripheral lymphocytes in autoimmune B6/gld mice

C57BL/6-gld/gld (B6/gld) mice have a point mutation in the gene for Fas ligand (FasL) resulting in nonfunctional FasL protein. We hypothesized that the lack of normal Fas/FasL interactions in these mice might result in abnormalities of Fas expression. Thus, we compared spleen cells from B6/gld mice and normal B6 control mice. While B6 spleen cells consisted of two main populations, Fashigh (high Fas expression) and Faslow (low Fas expression), nearly all B6/gld spleen cells were Fashigh. Two-color immunofluorescence revealed that the Fashigh and Faslow populations in the B6 spleen were Thy-1.2+ (T cells) and IgM+ (B cells), respectively, whereas both T cells and B cells in the B6/gld spleen were Fashigh, indicating that Fas expression is increased on B cells in the B6/gld spleen. This phenomenon was age related and restricted to peripheral lymphocytes. In addition to Fas, B6/gld splenic B cells showed increased expression of the costimulatory molecule B7-2, while the related costimulatory molecule B7-1 was up-regulated on both B cells and T cells in the B6/gld spleen. In vitro, both B cells and T cells from the B6/gld spleen showed an increase in susceptibility to apoptosis mediated by soluble anti-Fas Ab. These results suggest that some lymphocytes in B6/gld mice are primed to undergo Fas-mediated apoptosis, but are unable to do so due to the absence of functional FasL. Further study of such abnormal lymphocytes in the B6/gld spleen may elucidate the nature of autoimmunity in these mice.

Endothelial cell expression of intercellular adhesion molecule 1 in experimental posthemorrhagic vasospasm

OBJECTIVE

The exposure of large intracranial arteries to blood after an aneurysmal subarachnoid hemorrhage leads to a cascade of morphological and physiological changes in the vessels, a condition generally described as vasospasm. This response to the periadventitial deposition of blood is mediated in part by the endothelial layer of the vessel. This study was undertaken to examine the role of endothelial cell expression of intercellular adhesion molecule 1 (ICAM-1) in the initiation and regulation of this response.

METHODS

The femoral artery model of vasospasm was used in rats (65 animals, 130 arteries). In each rat, one artery was exposed to blood and the contralateral vessel was exposed to saline, so that each animal served as its own control. Animals were perfused and killed at sequential time points, from 1 hour to 20 days after blood exposure. The vessels were examined immunohistochemically and histologically for the presence of ICAM-1 and morphological features of vasospasm, respectively.

RESULTS

Endothelial cell ICAM-1 immunoreactivity was extensively increased in only the blood-exposed vessels, beginning 3 hours after clot placement and persisting for 24 hours. ICAM-1 immunoreactivity returned to baseline by 48 hours after blood exposure. The influx of inflammatory cells correlated directly with the time and location of increased ICAM-1 expression. Peak arterial remodeling was observed on the blood-exposed side 8 to 12 days after clot placement, as quantified by measurements of increased wall thickness, decreased lumen size, and increased collagen content.

CONCLUSION

Endothelial cell ICAM-1 expression seems to be an early and specific signal used by a vessel in response to the deposition of blood periadventitially. This molecule may be a marker for vessels likely to undergo subsequent morphological remodeling and vasospasm.

B cell genotype determines the fine specificity of autoantibody in lpr mice

Anti-Sm Abs are specific markers of human systemic lupus erythematosus (SLE) and of murine models of this disease. In humans, anti-Sm Abs are mostly IgG1, and in MRL/lpr mice, IgG2a; both are T-dependent isotypes. Other lpr strains, such as B6/lpr, do not produce anti-Sm Ab spontaneously. The present study was aimed at identifying the cellular expression of background genes responsible for generation of the anti-Sm Ab response in MRL/lpr mice. We used double chimeric mice made by transferring MRL/lpr and B6/lpr bone marrows into irradiated allotype heterozygous F1 mice. Five mo after reconstitution, FACS analysis of lymph node (LN) and spleen cells revealed that both MRL/lpr and B6/lpr cells coexisted in roughly equal numbers. Ab produced by each donor could be distinguished by allotype-specific assays. IgG2a anti-Sm was made only by MRL-derived B cells despite the presence of T cells that might potentially provide help to the B6/lpr B cells. The frequency of anti-Sm Ab-producing individuals was similar to that of unmanipulated MRL/lpr mice (about 25%). IgG2a anti-chromatin and total IgG2a was mostly dominated by the MRL-derived B cells. B6-derived B cells produced more rheumatoid factor (RF) against their own IgG2b(b), while RF against IgG2a was dominated by MRL-derived B cells. This suggests that the control of the production of particular autoantibody specificities, such as anti-Sm, is determined by the expression of MRL or B6 background genes in B cells.

B cell genotype determines the fine specificity of autoantibody in lpr mice

Anti-Sm Abs are specific markers of human systemic lupus erythematosus (SLE) and of murine models of this disease. In humans, anti-Sm Abs are mostly IgG1, and in MRL/lpr mice, IgG2a; both are T-dependent isotypes. Other lpr strains, such as B6/lpr, do not produce anti-Sm Ab spontaneously. The present study was aimed at identifying the cellular expression of background genes responsible for generation of the anti-Sm Ab response in MRL/lpr mice. We used double chimeric mice made by transferring MRL/lpr and B6/lpr bone marrows into irradiated allotype heterozygous F1 mice. Five mo after reconstitution, FACS analysis of lymph node (LN) and spleen cells revealed that both MRL/lpr and B6/lpr cells coexisted in roughly equal numbers. Ab produced by each donor could be distinguished by allotype-specific assays. IgG2a anti-Sm was made only by MRL-derived B cells despite the presence of T cells that might potentially provide help to the B6/lpr B cells. The frequency of anti-Sm Ab-producing individuals was similar to that of unmanipulated MRL/lpr mice (about 25%). IgG2a anti-chromatin and total IgG2a was mostly dominated by the MRL-derived B cells. B6-derived B cells produced more rheumatoid factor (RF) against their own IgG2b(b), while RF against IgG2a was dominated by MRL-derived B cells. This suggests that the control of the production of particular autoantibody specificities, such as anti-Sm, is determined by the expression of MRL or B6 background genes in B cells.

Radiation and stress-induced apoptosis: a role for Fas/Fas ligand interactions

The lpr gene encodes a defective form of Fas, a cell surface protein that mediates apoptosis. This defect blocks apoptotic deletion of autoreactive T and B cells, leading to lymphoproliferation and lupus-like autoantibody production. The effects of the lpr Fas mutation on other kinds of physiologically relevant apoptosis are largely undocumented. To assess whether some of the apoptosis known to occur after ionizing radiation might be mediated by Fas/Fas ligand (FasL) interactions, we quantitated in vitro apoptosis by flow cytometry measurement of DNA content in splenic T and B cells from irradiated 5- to 8-month-old B6/lpr mice. Total apoptosis of both lpr and control cells was substantial after treatment; however there was a significant difference between B6 (73%) and lpr (25%) lymphocyte apoptosis. Thy1, CD4, CD8, and IgM cells from lpr showed much lower levels of apoptosis than control cells after irradiation. Apoptosis induced by heat shock was also impaired in lpr. The finding that gamma-irradiation increased Fas expression on B6 cells and that irradiation-induced apoptosis could be blocked with a Fas-Fc fusion protein further supported the possible involvement of Fas in this form of apoptosis. Fas/FasL interactions may thus play an important role in identifying and eliminating damaged cells after gamma-irradiation and other forms of injury.

Fas-dependent CD4+ cytotoxic T-cell-mediated pathogenesis during virus infection

beta 2-Microglobulin-deficient (beta 2m-) mice generate a CD4+ major histocompatibility complex class II-restricted cytotoxic T-lymphocyte (CTL) response following infection with lymphocytic choriomeningitis (LCM) virus (LCMV). We have determined the cytotoxic mechanism used by these CD4+ CTLs and have examined the role of this cytotoxic activity in pathogenesis of LCM disease in beta 2m- mice. Lysis of LCMV-infected target cells by CTLs from beta 2m- mice is inhibited by addition of soluble Fas-Ig fusion proteins or by pretreatment of the CTLs with the protein synthesis inhibitor emetine. In addition, LCMV-infected cell lines that are resistant to anti-Fas-induced apoptosis are refractory to lysis by these virus-specific CD4+ CTLs. These data indicate that LCMV-specific CD4+ CTLs from beta 2m- mice use a Fas-dependent lytic mechanism. Intracranial (i.c.) infection of beta 2m- mice with LCMV results in loss of body weight. Fas-deficient beta 2m- Jpr mice develop a similar wasting disease following i.c. infection. This suggests that Fas-dependent cytotoxicity is not required for LCMV-induced weight loss. A potential mediator of this chronic wasting disease is tumor necrosis factor (TNF)-alpha, which is produced by LCMV-specific CD4+ CTLs. In contrast to LCMV-induced weight loss, lethal LCM disease in beta 2m- mice is dependent on Fas-mediated cytotoxicity. Transfer of immune splenocytes from LCMV-infected beta 2m- mice into irradiated infected beta 2m- mice results in death of recipient animals. In contrast, transfer of these splenocytes into irradiated infected beta 2m- Jpr mice does not cause death. Thus a role for CD4+ T-cell-mediated cytotoxicity in virus-induced immunopathology has now been demonstrated.

Both Sm and DNA are selecting antigens in the anti-Sm B cell response in autoimmune MRL/lpr mice

More than half of the anti-Sm hybridomas isolated from MRL/Mp-lpr/lpr (MRL/lpr) mice produce Abs that also bind ssDNA, and half of these bind dsDNA. Intraclonal comparisons indicate that DNA is a selecting Ag for at least some dual-binding clones. To determine whether Sm itself is a selecting Ag for anti-Sm, we have identified the somatic mutations within the expressed VH and V kappa genes of eight anti-Sm hybridomas, six of which do not bind DNA. We find these V genes have between 0 and 12 somatic mutations each, and that four hybridomas possess a higher number of heavy or light chain CDR replacement (R) mutations than expected by chance, suggesting that these anti-Sm-producing B cells have undergone Ag selection. To demonstrate directly the effect of somatic mutation on Sm binding, we have engineered the unmutated counterpart of Ab 2-12, an Sm-specific hybridoma Ab with a nonrandom distribution of V kappa CDR R mutations, and compared its ability to bind Sm and ssDNA with that of the originally isolated 2-12 Ab. We find that the unmutated Ab has a much lower avidity for Sm than the mutant, but, unlike the mutant, it binds ssDNA. We conclude that Sm can drive clonal expansion in the anti-Sm response, and that Sm-only binding B cells can arise from Sm/DNA dual-binding B cell clonal precursors. These data also suggest that dual binding is not necessary to sustain clonal expansion. Thus, this response is unique in that it can be driven by either of two Ags.

Both Sm and DNA are selecting antigens in the anti-Sm B cell response in autoimmune MRL/lpr mice

More than half of the anti-Sm hybridomas isolated from MRL/Mp-lpr/lpr (MRL/lpr) mice produce Abs that also bind ssDNA, and half of these bind dsDNA. Intraclonal comparisons indicate that DNA is a selecting Ag for at least some dual-binding clones. To determine whether Sm itself is a selecting Ag for anti-Sm, we have identified the somatic mutations within the expressed VH and V kappa genes of eight anti-Sm hybridomas, six of which do not bind DNA. We find these V genes have between 0 and 12 somatic mutations each, and that four hybridomas possess a higher number of heavy or light chain CDR replacement (R) mutations than expected by chance, suggesting that these anti-Sm-producing B cells have undergone Ag selection. To demonstrate directly the effect of somatic mutation on Sm binding, we have engineered the unmutated counterpart of Ab 2-12, an Sm-specific hybridoma Ab with a nonrandom distribution of V kappa CDR R mutations, and compared its ability to bind Sm and ssDNA with that of the originally isolated 2-12 Ab. We find that the unmutated Ab has a much lower avidity for Sm than the mutant, but, unlike the mutant, it binds ssDNA. We conclude that Sm can drive clonal expansion in the anti-Sm response, and that Sm-only binding B cells can arise from Sm/DNA dual-binding B cell clonal precursors. These data also suggest that dual binding is not necessary to sustain clonal expansion. Thus, this response is unique in that it can be driven by either of two Ags.

MHC genes modify systemic autoimmune disease. The role of the I-E locus

The MHC exerts an important influence on systemic autoimmune disease. In C57BL/6-lpr/lpr (B6/lpr) mice, substitution of the H-2d instead of the H-2b MHC haplotype results in a global reduction in autoantibody levels. Since H-2d expresses both I-A and I-E, while H-2b expresses only I-A, general down-regulation of autoimmunity in the d haplotype might be due to I-E expression. This was tested with I-E alpha d transgenic B6/lpr mice, which expressed a functional surface I-E molecule. Five-month-old transgene-positive B6/lpr mice had much lower total IgG, IgG anti-chromatin, anti-DNA, and IgM rheumatoid factor directed against IgG1 and against IgG2b than transgene-negative littermates (p < or = 0.002), as well as significantly lower spleen and lymph node weights (p < or = 0.002). Decreases in autoantibody levels in the transgenic lpr mice were not due to a nonspecific effect of the I-E alpha d transgene, since transgene-positive B6/lpr.H-2d mice had levels of autoantibodies comparable with transgene-negative B6/lpr.H-2d mice. To determine whether autoantibody was preferentially made by I-E-negative B cells, irradiated (B6/lpr.Igha x B6/lpr.I-E alpha d)F1 mice were reconstituted with equal amounts of B6/lpr.Igha and B6/lpr.I-E alpha d bone marrow. Allotype-specific ELISA showed that most autoantibody was produced by the I-E negative B cells (range 97% to 84%). The results show that a functional I-E molecule in lpr mice leads to generalized reduction in autoantibody levels through a direct effect on the B cell. The molecular mechanism of this effect remains to be determined.

MHC genes modify systemic autoimmune disease. The role of the I-E locus

The MHC exerts an important influence on systemic autoimmune disease. In C57BL/6-lpr/lpr (B6/lpr) mice, substitution of the H-2d instead of the H-2b MHC haplotype results in a global reduction in autoantibody levels. Since H-2d expresses both I-A and I-E, while H-2b expresses only I-A, general down-regulation of autoimmunity in the d haplotype might be due to I-E expression. This was tested with I-E alpha d transgenic B6/lpr mice, which expressed a functional surface I-E molecule. Five-month-old transgene-positive B6/lpr mice had much lower total IgG, IgG anti-chromatin, anti-DNA, and IgM rheumatoid factor directed against IgG1 and against IgG2b than transgene-negative littermates (p &lt; or = 0.002), as well as significantly lower spleen and lymph node weights (p &lt; or = 0.002). Decreases in autoantibody levels in the transgenic lpr mice were not due to a nonspecific effect of the I-E alpha d transgene, since transgene-positive B6/lpr.H-2d mice had levels of autoantibodies comparable with transgene-negative B6/lpr.H-2d mice. To determine whether autoantibody was preferentially made by I-E-negative B cells, irradiated (B6/lpr.Igha x B6/lpr.I-E alpha d)F1 mice were reconstituted with equal amounts of B6/lpr.Igha and B6/lpr.I-E alpha d bone marrow. Allotype-specific ELISA showed that most autoantibody was produced by the I-E negative B cells (range 97% to 84%). The results show that a functional I-E molecule in lpr mice leads to generalized reduction in autoantibody levels through a direct effect on the B cell. The molecular mechanism of this effect remains to be determined.

Phenotypic abnormalities of splenic and bone marrow B cells in lpr and gld mice

Mice homozygous for the mutant Fas gene lpr develop generalized lymphoproliferation and produce autoantibodies resembling those found in human SLE. We have previously shown that these autoantibodies are produced by B2 cells rather than B1 cells and that the autoantibody- producing B cells are intrinsically abnormal. We investigated further the lpr B cell with a large panel of antibodies to B-cell surface markers to identify phenotypic abnormalities. B cells from spleen and bone marrow of age-matched congenic mice differing only at the lpr locus were examined by flow cytometry. Two consistent phenotypic differences were identified. First, spleen cells from older lpr mice had an increase in the number and percentage of IgM+ B cells expressing low levels of CD23. Second, lpr bone marrow had decreased numbers of B220hiIgM+-syndecan-1+CD23+ B cells. All other markers tested, except the previously identified modest increase of Ia on lpr spleen cells, showed no consistent differences. B cells from gld mice showed the same phenotypic abnormalities as those from lpr. Compared to T cells, the relative paucity of cell surface marker differences between lpr and +/+ B cells suggests that B cells may have fewer regulatory mechanisms to silence autoreactive specificities. The phenotypic differences identified may provide clues to the mechanism of autoantibody production in lpr mice, while the overwhelming phenotypic similarity between lpr and +/+ B cells suggests that the major abnormality of lpr B cells may lie in their specificity, that is, in their inability to delete autoreactive subsets.

Suppression and reversal of gld disease by parabiosis with normal mice

The disruption of the Fas receptor or Fas ligand by the lpr or gld mutations, respectively, results in severe autoimmune and lymphoproliferative disease due to the failure of Fas-mediated deletion of self-reactive lymphocytes. Recently, we have shown in mixed chimeras that gld-induced autoimmunity could be corrected by normal bone marrow, in particular by normal T cells. In contrast, lpr-mediated autoimmunity could not be influenced by normal bone marrow-derived cells. In the present report, we have studied the role of normal lymphocytes in suppressing or reversing gld-induced autoimmunity by parabiosis with normal mice. Our results show a suppression of lymphadenopathy, fewer CD4-CD8- T cells, and lower levels of autoantibody production in gld mice parabiosed with normal mice at 4-6 weeks of age. The gld mice parabiosed with normal mice at 4 months of age also exhibited a substantial reduction of both total and CD4-CD8- T cells in the periphery 2 months after surgery. However, they showed little reduction of autoantibodies compared to gld mice parabiosed with gld mice. In contrast, older lpr mice did not exhibit any reduction in lymphadenopathy or autoantibody production after parabiosis with normal mice. The prevention or reversal of lymphadenopathy in parabiosed gld mice suggests that ongoing Fas-mediated deletion in the periphery may play an important role in maintaining self-tolerance. The relative irreversibility of autoantibody synthesis in older parabiosed gld mice suggests that autoantibody-producing B cells or their committed precursors are long lived and do not express functional Fas receptor.

The Yaa gene-mediated acceleration of murine lupus: Yaa- T cells from non-autoimmune mice collaborate with Yaa+ B cells to produce lupus autoantibodies in vivo

The BXSB Y chromosome-linked mutant gene, Yaa, promotes autoimmune responses in mice predisposed to a lupus-like autoimmune disease. We have previously shown that a cognate interaction of T cells with B cells expressing the Yaa gene appears to be responsible for the accelerated production of autoantibodies. To investigate whether T cells that provide help for autoantibody production by Yaa+ B cells need to express the Yaa gene, we have made radiation bone marrow chimeras containing two sets of T and B cells from mice with or without the Yaa gene and differing by the Thy-1 and Igh allotypes. We then determined autoantibody production following the selective elimination of T cells of Yaa+ origin by treating mice with allele-specific anti-Thy-1 monoclonal antibody. Our results demonstrated that the selective production of autoantibodies by Yaa+ B cells in Yaa(+)-Yaa- double bone marrow chimeras can be mediated as efficiently by T cells from non-autoimmune mice lacking the Yaa gene as by T cells from autoimmune mice bearing the Yaa gene. This indicates that T cells from non-autoimmune Yaa- mice are capable of providing help for autoimmune responses by collaborating with Yaa+ B cells. These data thus strongly suggest that the Yaa gene defect is not functionally expressed in T cells, but only in B cells, and contrast with parallel experiments in the lpr model, in which defects of the Fas antigen in both T and B cells are crucial for the lpr gene-mediated promotion of autoantibody production.

bcl-2 transgenic Lpr mice show profound enhancement of lymphadenopathy

The lpr gene encodes a defective form of the fas gene that mediates apoptosis, and its expression results in autoantibodies and massive lymphadenopathy. bcl-2, another gene locus that affects programmed cell death, acts to inhibit apoptosis. Since multiple mechanisms controlling programmed cell death may contribute to systemic autoimmunity, the effect of the bcl-2 transgene on the lpr model was examined by crossing bcl-2 transgenic and C57BL/6-lpr mice. Compared with bcl-2-/lpr mice, bcl-2+/lpr showed dramatic increases in lymphadenopathy and T cell accumulation, but not in autoantibodies or B cell numbers. Short term transfer studies demonstrated that double negative T cells normally have a limited lifespan, and their survival is enhanced by the bcl-2 transgene. Thus, defects in separate apoptosis mechanisms may combine to produce enhanced pathologic effects.

bcl-2 transgenic Lpr mice show profound enhancement of lymphadenopathy

The lpr gene encodes a defective form of the fas gene that mediates apoptosis, and its expression results in autoantibodies and massive lymphadenopathy. bcl-2, another gene locus that affects programmed cell death, acts to inhibit apoptosis. Since multiple mechanisms controlling programmed cell death may contribute to systemic autoimmunity, the effect of the bcl-2 transgene on the lpr model was examined by crossing bcl-2 transgenic and C57BL/6-lpr mice. Compared with bcl-2-/lpr mice, bcl-2+/lpr showed dramatic increases in lymphadenopathy and T cell accumulation, but not in autoantibodies or B cell numbers. Short term transfer studies demonstrated that double negative T cells normally have a limited lifespan, and their survival is enhanced by the bcl-2 transgene. Thus, defects in separate apoptosis mechanisms may combine to produce enhanced pathologic effects.

Sm and DNA binding by dual reactive B cells requires distinct VH, V kappa, and VH CDR3 structures

We have previously demonstrated an overlap of the anti-Sm and anti-DNA responses in MRL/Mp-lpr/lpr mice. The Ab produced by many anti-Sm hybridomas bind DNA and are encoded by Ig V genes used by anti-DNA hybridomas. In addition, some anti-Sm Ab that bind DNA have acquired mutations that improve DNA binding, indicating that DNA is a selecting Ag in the anti-Sm response. To gain insight into the basis for the dual binding ability of these Ab, we coexpressed the H chain from the anti-Sm hybridoma 2-12 with nine different L chains. Hybridoma 2-12 binds Sm but not DNA, yet expresses the same J558 VH gene as three anti-Sm hybridomas that bind ssDNA and at least one anti-DNA hybridoma that does not bind Sm. We found that most of the transfectoma Ab bind Sm, but their avidities vary over more than 3 orders of magnitude. Five of the nine transfectoma Ab bind ssDNA, and none bind dsDNA. In general, the ability to bind each Ag follows the binding ability of the hybridoma from which the L chain is derived. H Chain swapping experiments indicate that the H chain, VH CDR3 in particular, contributes to the binding of both Sm and DNA. We conclude that Sm and DNA select for distinct features of VH, V kappa, and VH CDR3, suggesting selection by both Ag in the anti-Sm response.

Sm and DNA binding by dual reactive B cells requires distinct VH, V kappa, and VH CDR3 structures

We have previously demonstrated an overlap of the anti-Sm and anti-DNA responses in MRL/Mp-lpr/lpr mice. The Ab produced by many anti-Sm hybridomas bind DNA and are encoded by Ig V genes used by anti-DNA hybridomas. In addition, some anti-Sm Ab that bind DNA have acquired mutations that improve DNA binding, indicating that DNA is a selecting Ag in the anti-Sm response. To gain insight into the basis for the dual binding ability of these Ab, we coexpressed the H chain from the anti-Sm hybridoma 2-12 with nine different L chains. Hybridoma 2-12 binds Sm but not DNA, yet expresses the same J558 VH gene as three anti-Sm hybridomas that bind ssDNA and at least one anti-DNA hybridoma that does not bind Sm. We found that most of the transfectoma Ab bind Sm, but their avidities vary over more than 3 orders of magnitude. Five of the nine transfectoma Ab bind ssDNA, and none bind dsDNA. In general, the ability to bind each Ag follows the binding ability of the hybridoma from which the L chain is derived. H Chain swapping experiments indicate that the H chain, VH CDR3 in particular, contributes to the binding of both Sm and DNA. We conclude that Sm and DNA select for distinct features of VH, V kappa, and VH CDR3, suggesting selection by both Ag in the anti-Sm response.

Expression of Hodgkin's disease associated antigen BLA.36 in anaplastic large cell lymphomas and lymphomatoid papulosis primarily of T-cell origin

Monoclonal antibody BLA.36 stains Reed-Sternberg (RS) cells and their mononuclear variants, as well as some benign and malignant cells of B-cell lineage, and retains its immunoreactivity in formalin- and B5-fixed tissue. The origin of the RS cell is controversial and the distinction between Hodgkin's disease (HD), anaplastic large cell lymphoma (ALCL), and lymphomatoid papulosis (LyP) (the latter two primarily T-cell in origin), can be difficult. The authors studied expression of BLA.36 in 22 cases of ALCL, 13 cases of LyP, and 15 cases of HD. Most atypical or malignant cells stained for BLA.36 in 10 of 22 cases of ALCL, 9 of 13 cases of LyP, and 9 of 15 cases of HD. Additional immunohistochemistry or gene rearrangement analysis indicated a T-cell origin for 8 of 10 BLA.36 positive ALCL, and 9 of 9 BLA.36 positive LyP cases. BLA.36 was expressed by T-cell lines derived from two ALCLs and one CD30+ cell line derived from LyP. The authors conclude that BLA.36 is not specific for lymphomas of B-cell origin and cannot be used to distinguish between HD, ALCL, and LyP with RS-like cells. These results further support a relationship between HD, ALCL, and LyP and suggest that RS cells are histogenetically related to both B- and T-lymphocytes.

Absence of autoantigen Ku in mature human neutrophils and human promyelocytic leukemia line (HL-60) cells and lymphocytes undergoing apoptosis

The Ku autoantigen is a heterodimer of 70- and 80-kD proteins recognized by autoantibodies from patients with systemic lupus erythematosus and related diseases that is the DNA-binding component of a DNA-dependent protein kinase. The catalytic activity of DNA-dependent protein kinase is carried by a 350-kD subunit (p350). In light of the recently described role of Ku in repairing double-strand DNA breaks, we investigated the regulation of Ku and p350 levels in neutrophils, a terminally differentiated cell type destined to undergo apoptosis. Since the appearance of double-strand DNA breaks is characteristic of apoptosis, we were interested in the possibility that Ku might oppose programmed cell death. Analysis of peripheral blood cells by flow cytometry using anti-Ku and anti-p350 monoclonal antibodies revealed that neutrophils were unstained, whereas resting (G0) lymphocytes were positive. The absence of Ku in mature neutrophils was confirmed by Western blotting and enzyme-linked immunosorbent assay for Ku antigen. In contrast, the human promyelocytic leukemia line, HL-60, which undergoes differentiation toward neutrophils after dimethylsulfoxide treatment, was positive for Ku and p350. In view of the short lifespan of neutrophils and the prolonged half-life of Ku and p350 (> 5 d), these data suggested that Ku was actively degraded during myeloid differentiation. Analysis of HL-60 cells by flow cytometry revealed that Ku staining was bimodal. Cells in G1/G0, S, or G2/M were all stained positively, whereas cells with a subdiploid DNA content characteristic of apoptosis were Ku negative. Similar results were obtained with phytohemagglutin-stimulated human lymphocytes. These data suggest that the Ku antigen is actively degraded in both myeloid cells destined to undergo apoptosis and apoptotic lymphocytes, raising the possibility that degradation of Ku may help to prevent the inappropriate repair of fragmented nuclear DNA during apoptosis.