Immunoglobulin M nephropathy nephropathy in adults and adolescents in India: a single-center study of natural history.

BACKGROUND: Immunoglobulin M nephropathy (IgMN) is an idiopathic glomerulonephritis (GN) usually presenting clinically as steroid resistant/dependent nephrotic syndrome (NS) with pathology of mesangial proliferative GN or focal and segmental glomerulosclerosis with diffuse predominant mesangial IgM deposits. Not much information is available about its natural history. This is the first Indian study to our knowledge on IgMN in adults and adolescents. MATERIALS AND METHODS: We evaluated renal biopsies performed at our center between January,'04 to September,'09. Biopsies of all adolescents and adults were evaluated for IgMN and we studied their age, gender distribution, blood pressure (BP), disease duration, steroid/immunosuppressive management and serial serum creatinine (SCr), urinary proteins, and BP values. Patients with other systemic diseases/infections and children were excluded. RESULTS: IgMN constituted 4.3% of 2702 adult renal biopsies. No significant gender predilection was noted. Males presented at average age of 23.1 years, females at 30 years. Steroid-dependent NS was the commonest presentation noted in 75% followed by steroid-resistant NS. Hypertension was noted in 10% patients. Mesangial proliferative GN (MePGN) was commonest histopathological finding noted in 74.4%, followed by focal segmental glomerulosclerosis (FSGS) in 16.2%, and minimal change disease (MCD) in 9.4% biopsies. Sole IgM deposits were noted in 88.5%. All MCD, 35.6% MePGN reached remission, FSGS progressed to renal failure by 1 year. Hypertension, proteinuria, interstitial fibrosis, and FSGS were bad prognosticators. CONCLUSIONS: This is the first Indian study of IgMN in adults and adolescents carried out over a period of 5.8 years, which has shown that hypertension, proteinuria, and interstitial fibrosis at presentation have bad prognosis.

Immunoglobulin M antiplatelet autoantibodies from mice immunized with rat platelets induce thrombocytopenia and platelet function impairment.

Antiplatelet monoclonal autoantibodies (mAbs) were derived from CBA mice immunized with rat platelets. Two IgM antiplatelet mAbs were further analyzed. L1C43 mAb bound a 150-160 kDa antigen, recognized activated platelets better than resting ones and impaired platelet adhesion, but not clot retraction. L1H31 mAb recognized a ±95 kDa molecule, bound similarly activated and resting platelets and did not modify platelet adhesion, but inhibited clot retraction. Both mAbs induced in vivo thrombocytopenia most likely through phagocytosis of opsonized platelets. These autoreactive antibodies can thus induce both platelet destruction and impairment of their function. They are reflective of autoantibodies found in human patients and may serve for further analysis of antiplatelet autoantibody pathogenicity and mechanisms of autoimmune disease.

Preclinical in vitro and in vivo characterization of the fully human monoclonal IgM antibody KBPA101 specific for Pseudomonas aeruginosa serotype IATS-O11.

Pseudomonas aeruginosa infection in ventilator-associated pneumonia is a serious and often life-threatening complication in intensive care unit patients, and new treatment options are needed. We used B-cell-enriched peripheral blood lymphocytes from a volunteer immunized with a P. aeruginosa O-polysaccharide-toxin A conjugate vaccine to generate human hybridoma cell lines producing monoclonal antibodies specific for individual P. aeruginosa lipopolysaccharide serotypes. The fully human monoclonal antibody secreted by one of these lines, KBPA101, is an IgM/kappa antibody that binds P. aeruginosa of International Antigenic Typing System (IATS) serotype O11 with high avidity (5.81 x 10(7) M(-1) +/- 2.8 x 10(7) M(-1)) without cross-reacting with other serotypes. KBPA101 specifically opsonized the P. aeruginosa of IATS O11 serotype and mediated complement-dependent phagocytosis in vitro by the human monocyte-like cell line HL-60 at a very low concentration (half-maximal phagocytosis at 0.16 ng/ml). In vivo evaluation of KBPA101 demonstrated a dose-response relationship for protection against systemic infections in a murine burn wound sepsis model, where 70 to 100% of animals were protected against lethal challenges with P. aeruginosa at doses as low as 5 microg/animal. Furthermore, a high efficacy of KBPA101 in protection from local respiratory infections in an acute lung infection model in mice was demonstrated. Preclinical toxicology evaluation on human tissue, in rabbits, and in mice did not indicate any toxicity of KBPA101. Based on these preclinical findings, the first human clinical trials have been initiated.

Immunological property of antibodies against N-glycolylneuraminic acid epitopes in cytidine monophospho-N-acetylneuraminic acid hydroxylase-deficient mice.

The generation of pigs devoid of Galalpha1,3Galbeta1,4GlcNAc (Gal) residues has stimulated interest in non-Gal Ags as potentially important targets for Ab binding leading to rejection of pig organ xenografts in humans. Although N-glycolylneuraminic acid (NeuGc) epitopes, which are widely expressed on the endothelial cells of all mammals except humans, are likely targets of anti-non-Gal Abs, this aspect has not been investigated intensively owing to the absence of an appropriate animal model. In this study, we used CMAH(-/-) mice, which are completely deficient in NeuGc and thus produce anti-NeuGc Abs. Sera obtained from CMAH(-/-) mice and healthy human volunteers having anti-NeuGc Abs initiated complement-mediated lysis against CMAH(+/+) cells in vitro. The cytotoxic activity of anti-NeuGc Abs was also determined in vivo (i.e., NeuGc-expressing CMAH(+/+) mouse splenocytes that had been i.v. injected were completely eliminated in syngeneic CMAH(-/-) mice). CMAH(-/-) mice rejected the islets transplanted from syngeneic CMAH(+/+) mice. Thus, the anti-NeuGc Ab-mediated response may be crucially involved in xenograft loss. This is the first direct demonstration of the immunogenic property of NeuGc determinants as targets of the corresponding Abs in CMAH(+/+)-to-CMAH(-/-) transplantation setting.

Early pregnancy factor is required at two important stages of embryonic development in the mouse.

PROBLEM: The importance of early pregnancy factor (EPF) at the pre-implantation stage of development (days 1-3 post-coitum [p.c.]) has been previously established in this laboratory. However, the role of EPF at the implantation stage (days 4.5-5 p.c.) has not been determined. This present study therefore investigates the role of EPF at this important developmental stage, both in vivo and in vitro. METHOD OF STUDY: Mated mice were passively immunized with anti-EPF antibodies at the peri-implantation stage (days 3.5-4 p.c.) and embryo implantation recorded. Parallel studies were conducted in vitro, where the effect of anti-EPF antibodies on trophoblast outgrowth of blastocysts was determined. RESULTS: Administration of anti-EPF antibodies in vivo at the peri-implantation stage of development resulted in failure of embryos to implant. Similarly, trophoblastic outgrowth of blastocysts was adversely affected in the presence of anti-EPF antibodies. CONCLUSIONS: These results, together with previous findings that anti-EPF antibodies retard embryonic development when administered at the early pre-implantation stage, clearly demonstrate that EPF is required by the embryo at two important developmental stages- the one-two-cell stage and the peri-implantation stage.

Neutrophils do not mediate blood-brain barrier permeability early after controlled cortical impact in rats.

Controlled cortical impact (CCI) produces blood-brain barrier (BBB) permeability and an acute inflammatory response in injured brain, associated with upregulation of cell adhesion molecules and accumulation of neutrophils. Nevertheless, the role of acute inflammation in the pathogenesis of BBB permeability after traumatic brain injury (TBI) is undefined. The purpose of this study was to examine the time course of acute inflammation and BBB permeability after CCI in rats and to determine the effect of neutrophil depletion on BBB permeability early after CCI. In the first protocol, four groups of rats (n = 4-7/group) were subjected to CCI. Expression of endothelial (E)-selectin on cerebrovascular endothelium, accumulation of neutrophils, and BBB permeability were measured in brain at 1, 4, 8, and 24 hours after injury by immunohistochemistry or spectrophotometric quantification of Evans blue. E-selectin upregulation and neutrophil accumulation in injured brain occurred at later times than maximal BBB permeability. In a second protocol, rats made neutropenic with a murine monoclonal IgM antibody (RP-3) specific for rat neutrophils were subjected to CCI, given Evans blue at 3.5 hours, and sacrificed at 4 hours after injury. Neutrophil depletion did not affect BBB permeability at 4 hours after CCI. We conclude that events other than those mediated by neutrophils initiate BBB permeability early after CCI.

Complement-mediated anti-HIV-1 effect induced by human IgM monoclonal antibody against ganglioside GM2.

HIV-infected cells aberrantly express a high level of antigenic glycosidic structures such as GM2 and Gg4. Some normal sera containing natural IgM Abs to GM2 and/or Gg4 cause C-mediated cytolysis of HIV-infected cells. In the present study we demonstrated that a human IgM anti-GM2 mAb (L55 Ab) can induce cytolysis of HIV-infected cells. Increased GM2 expression by HIV-1 infection of a human T cell line (MOLT4), a human monocyte cell line (U937), and human lymphoblastoid cells was confirmed by immunofluorescence staining with L55 Ab. These infected cells were readily lysed by L55 Ab in the presence of fresh human serum as a C source that alone did not cause cytolysis. L55 Ab also had the ability to destroy HIV-1 particles via C-mediated lysis. By adding L55 Ab together with human C to mixed culture of HIV-infected cells and naive cells, HIV-1 replication was significantly suppressed, and this effect was synergistic when L55 Ab was combined with a reverse transcriptase inhibitor and a proteinase inhibitor. Therefore, a human IgM anti-GM2 mAb may be effective in treating HIV-infected patients, especially when used together with chemotherapeutic agents.

Anti-GM1/GD1b M-proteins damage human spinal cord neurons co-cultured with muscle.

IgM M-proteins in some motor neuron disease (MND) patients bind immunologically to shared determinants on gangliosides GM1 and GD1b. Since patients with these M-proteins have improved with immunotherapy the antibodies may be important in the pathogenesis of MND. To study how the M-proteins might damage motor neurons, we established co-cultures of human neurons from spinal cord explants and human myotubes. Antibodies from patient but not control serum bound to the cultured neurons. Neurons in co-cultures degenerated after incubation with patient but not control serum. These results demonstrate that anti-GM1 antibodies can bind to and destroy spinal cord neurons that are cultured with muscle. Nerve-muscle co-cultures can serve as a system to examine effects of anti-GM1/GD1b M-proteins on motor neurons.

Anti-B-series ganglioside-recognizing autoantibodies in an acute sensory neuropathy patient cause cell death of rat dorsal root ganglion neurons.

To examine the cytotoxicity of a patient's serum with an acute relapsing sensory neuropathy syndrome, dorsal root ganglion neurons from young adult rats were cultured in the presence of the patient's serum which had an extremely higher-titer monoclonal IgM antibody recognizing B-series gangliosides, GD2, GD1b, GT1b and GQ1b. By the addition of the inactivated patient's serum, the relatively larger cells died after undergoing of metamorphosis during several hours of culture, whilst the smaller cells survived. The IgM fraction isolated from the patient's serum showed similar cytotoxicity towards the neurons as the inactivated whole serum. No cytotoxicity was observed with the IgM fraction-containing medium after it had been absorbed with ganglioside GD1b. The results suggested that the anti-B-series ganglioside-directed antibody is the causal agent for the human neurologic disease.

Induction of experimental primary and secondary antiphospholipid syndromes in naive mice.

In the current series of experimental studies we show that anticardiolipin antibodies (ACA) are pathogenic: Infusion of serum ACA to the tail vein of naive mice induces experimental antiphospholipid syndrome (APLS) characterized by thrombocytopenia, prolonged aPTT, and recurrent fetal resorptions. Similar experimental APLS is induced by active immunization with serum as well as with natural human monoclonal ACA. APLS is also associated with low fecundity rate. The experimental APLS models were employed to demonstrate the efficacy of aspirin, low molecular heparin, and interleukin-3 preventing recurrent fetal loss. In another experiment, immunization with human monoclonal anti-DNA antibody was followed by the induction of APLS secondary to experimental systemic lupus erythematosus (SLE). In all studies, IgGs were found to be more pathogenic than IgMs ACA. These studies confirm the autoimmune nature of APLS.