The Role of IgM Antibodies in T Cell Lymphoma Protection in a Novel Model Resembling Anaplastic Large Cell Lymphoma.

MRL/lpr mice typically succumb to immune complex-mediated nephritis within the first year of life. However, MRL/lpr mice that only secrete IgM Abs because of activation-induced deaminase deficiency (AID-/-MRL/lpr mice) experienced a dramatic increase in survival. Further crossing of these mice to those incapable of making secretory IgM (µS mice) generated mice lacking any secreted Abs but with normal B cell receptors. Both strains revealed no kidney pathology, yet Ab-deficient mice still experienced high mortality. In this article, we report Ab-deficient MRL/lpr mice progressed to high-grade T cell lymphoma that can be reversed with injection of autoreactive IgM Abs or following adoptive transfer of IgM-secreting MRL/lpr B cells. Anti-nuclear Abs, particularly anti-dsDNA IgM Abs, exhibited tumor-killing activities against a murine T cell lymphoma cell line. Passive transfers of autoreactive IgM Abs into p53-deficient mice increased survival by delaying onset of T cell lymphoma. The lymphoma originated from a double-negative aberrant T cell population seen in MRL/lpr mice and most closely resembled human anaplastic large cell lymphoma. Combined, these results strongly implicate autoreactive IgM Abs in protection against T cell lymphoma.

Apoptotic Debris Accumulates on Hematopoietic Cells and Promotes Disease in Murine and Human Systemic Lupus Erythematosus.

Apoptotic debris, autoantibody, and IgG-immune complexes (ICs) have long been implicated in the inflammation associated with systemic lupus erythematosus (SLE); however, it remains unclear whether they initiate immune-mediated events that promote disease. In this study, we show that PBMCs from SLE patients experiencing active disease, and hematopoietic cells from lupus-prone MRL/lpr and NZM2410 mice accumulate markedly elevated levels of surface-bound nuclear self-antigens. On dendritic cells (DCs) and macrophages (MFs), the self-antigens are part of IgG-ICs that promote FcγRI-mediated signal transduction. Accumulation of IgG-ICs is evident on ex vivo myeloid cells from MRL/lpr mice by 10 wk of age and steadily increases prior to lupus nephritis. IgG and FcγRI play a critical role in disease pathology. Passive transfer of pathogenic IgG into IgG-deficient MRL/lpr mice promotes the accumulation of IgG-ICs prior to significant B cell expansion, BAFF secretion, and lupus nephritis. In contrast, diminishing the burden IgG-ICs in MRL/lpr mice through deficiency in FcγRI markedly improves these lupus pathologies. Taken together, our findings reveal a previously unappreciated role for the cell surface accumulation of IgG-ICs in human and murine lupus.

A smad signaling network regulates islet cell proliferation.

Pancreatic ß-cell loss and dysfunction are critical components of all types of diabetes. Human and rodent ß-cells are able to proliferate, and this proliferation is an important defense against the evolution and progression of diabetes. Transforming growth factor-ß (TGF-ß) signaling has been shown to affect ß-cell development, proliferation, and function, but ß-cell proliferation is thought to be the only source of new ß-cells in the adult. Recently, ß-cell dedifferentiation has been shown to be an important contributory mechanism to ß-cell failure. In this study, we tie together these two pathways by showing that a network of intracellular TGF-ß regulators, smads 7, 2, and 3, control ß-cell proliferation after ß-cell loss, and specifically, smad7 is necessary for that ß-cell proliferation. Importantly, this smad7-mediated proliferation appears to entail passing through a transient, nonpathologic dedifferentiation of ß-cells to a pancreatic polypeptide-fold hormone-positive state. TGF-ß receptor II appears to be a receptor important for controlling the status of the smad network in ß-cells. These studies should help our understanding of properly regulated ß-cell replication.

Altered pattern of immunoglobulin hypermutation in mice deficient in Slip-GC protein.

We recently identified a novel germinal center GTPase, SLIP-GC, that localizes to replication factories in B cells and that, when reduced, induces DNA breaks in lymphoma B cell lines in an activation-induced deaminase (AID)-dependent manner. Herein, we generated mice deficient in SLIP-GC and examined the impact of SLIP-GC deficiency in immunoglobulin hypermutation and class switch recombination, both AID-dependent mechanisms. SLIP-GC-deficient mice experienced a substantial increase in mutations at G:C base pairs at the region downstream of JH4 in the immunoglobulin heavy chain locus. This change was reflected in the overall mutation frequency, and it was associated with an increase in transitions from G:C base pairs, a hallmark of AID-mediated deamination during replication. In addition, G:C transitions at non-immunoglobulin loci also increased in these mice. Given the intracellular localization of SLIP-GC to sites of replicating DNA, these results suggest that SLIP-GC protects replicating DNA from AID-mediated deamination of cytosines in both strands.

Speckled-like pattern in the germinal center (SLIP-GC), a nuclear GTPase expressed in activation-induced deaminase-expressing lymphomas and germinal center B cells.

We identified a novel GTPase, SLIP-GC, with expression limited to a few tissues, in particular germinal center B cells. It lacks homology to any known proteins, indicating that it may belong to a novel family of GTPases. SLIP-GC is expressed in germinal center B cells and in lymphomas derived from germinal center B cells such as large diffuse B cell lymphomas. In cell lines, SLIP-GC is expressed in lymphomas that express activation-induced deaminase (AID) and that likely undergo somatic hypermutation. SLIP-GC is a nuclear protein, and it localizes to replication factories. Reduction of SLIP-GC levels in the Burkitt lymphoma cell line Raji and in non-Hodgkin lymphoma cell lines resulted in an increase in DNA breaks and apoptosis that was AID-dependent, as simultaneous reduction of AID abrogated the deleterious effects of SLIP-GC reduction. These results strongly suggest that SLIP-GC is a replication-related protein in germinal center B cells whose reduction is toxic to cells through an AID-dependent mechanism.

Abrogation of lupus nephritis in activation-induced deaminase-deficient MRL/lpr mice.

We generated MRL/lpr mice deficient in activation-induced deaminase (AID). Because AID is required for Ig hypermutation and class switch recombination, these mice lack hypermutated IgG Abs. Unlike their AID wild-type littermates, AID-deficient MRL/lpr mice not only lacked autoreactive IgG Abs but also experienced a dramatic increase in the levels of autoreactive IgM. This phenotype in AID-deficient mice translated into a significant reduction in glomerulonephritis, minimal mononuclear cell infiltration in the kidney, and a dramatic increase in survival to levels comparable to those previously reported for MRL/lpr mice completely lacking B cells and well below those of mice lacking secreted Abs. Therefore, this study wherein littermates with either high levels of autoreactive IgM or autoreactive IgG were directly examined proves that autoreactive IgM Abs alone are not sufficient to promote kidney disease in MRL/lpr mice. In addition, the substantial decrease in mortality combined with a dramatic increase in autoreactive IgM Abs in AID-deficient MRL/lpr mice suggest that autoreactive IgM Abs might not only fail to promote nephritis but may also provide a protective role in MRL/lpr mice. This novel mouse model containing high levels of autoreactive, unmutated IgM Abs will help delineate the contribution of autoreactive IgM to autoimmunity.

Known components of the immunoglobulin A:T mutational machinery are intact in Burkitt lymphoma cell lines with G:C bias.

The basis for mutations at A:T base pairs in immunoglobulin hypermutation and defining how AID interacts with the DNA of the immunoglobulin locus are major aspects of the immunoglobulin mutator mechanism where questions remain unanswered. Here, we examined the pattern of mutations generated in mice deficient in various DNA repair proteins implicated in A:T mutation and found a previously unappreciated bias at G:C base pairs in spectra from mice simultaneously deficient in DNA mismatch repair and uracil DNA glycosylase. This suggests a strand-biased DNA transaction for AID delivery which is then masked by the mechanism that introduces A:T mutations. Additionally, we asked if any of the known components of the A:T mutation machinery underscore the basis for the paucity of A:T mutations in the Burkitt lymphoma cell lines, Ramos and BL2. Ramos and BL2 cells were proficient in MSH2/MSH6-mediated mismatch repair, and express high levels of wild-type, full-length DNA polymerase eta. In addition, Ramos cells have high levels of uracil DNA glycosylase protein and are proficient in base excision repair. These results suggest that Burkitt lymphoma cell lines may be deficient in an unidentified factor that recruits the machinery necessary for A:T mutation or that AID-mediated cytosine deamination in these cells may be processed by conventional base excision repair truncating somatic hypermutation at the G:C phase. Either scenario suggests that cytosine deamination by AID is not enough to trigger A:T mutation, and that additional unidentified factors are required for full spectrum hypermutation in vivo.

Decreased frequency and highly aberrant spectrum of ultraviolet-induced mutations in the hprt gene of mouse fibroblasts expressing antisense RNA to DNA polymerase zeta.

In the budding yeast Saccharomyces cerevisiae, DNA polymerase zeta (pol zeta) is responsible for the great majority of mutations generated during error-prone translesion replication of DNA that contains UV-induced lesions. The catalytic subunit of pol zeta is encoded by the Rev3 gene. The orthologue of Rev3 has been cloned from higher eukaryotic cells, including human, but its role in mutagenesis and carcinogenesis remains obscure. Investigation into the cellular function of pol zeta has been hindered by the fact that Rev3 knockout mice do not survive beyond midgestation, and embryonic stem cells used to derive these mice are not genetically stable. We have generated a transgenic mouse that expresses antisense RNA transcripts to mRev3 endogeneous RNA. These mice are viable, have greatly reduced levels of Rev3 transcript, and have reduced levels of B cells and impaired development of high-affinity memory B cells. Here, we report that exposure of fibroblasts derived from these mice to UV resulted in a 4-5-fold reduction in mutant frequency at the hprt locus at every dose examined, and the mutation spectrum was highly aberrant compared with the control cells. In the control cells, 80% of the mutations were transitions and approximately 75% of these arose from photoproducts in the putative leading strand template. Strikingly, in transgenic cells, most of the mutations were transversions and there was a complete loss of strand bias. This mutation spectrum is highly aberrant and is similar to that induced by UV in human xeroderma pigmentosum variant cells, which lack polymerase eta. These data indicate that most UV-induced mutations are dependent on DNA pol zeta, a function that has been conserved from yeast to higher eukaryotic cells. However, in mammalian cells, other DNA polymerase(s) may accomplish error-prone translesion replication and are responsible for residual UV mutagenesis observed in the absence of pol zeta. Further, these data support a central role for DNA polymerase eta in the error-free bypass of UV photoproducts. The antisense Rev3 mice should be a useful model to study mutagenic lesion bypass by pol zeta in mammalian cells and to investigate the role this polymerase plays in carcinogenesis.

Mutagenesis by AID, a molecule critical to immunoglobulin hypermutation, is not caused by an alteration of the precursor nucleotide pool.

The novel cytidine deaminase, AID, plays a critical role in immunoglobulin (Ig) hypermutation. Its possible modes of action include deamination of an RNA transcript that encodes a molecule involved in these processes, deamination of the DNA encoding the variable regions of immunoglobulin genes, or deamination of monomeric cytidine or deoxycytidine (dC) nucleotide generating a mutagenic imbalanced nucleotide pool. We transformed AID into Escherichia coli cells and measured the nucleotide pools at 2 and 6h following induction of expression. Although the majority of the cells expressed AID at the relevant time points, the nucleotide pools were unaltered. In addition, mutagenesis by AID expression in E. coli was not synergistically enhanced in a bacterial strain defective in dUTPase, an enzyme that prevents accumulation of dUTP in the nucleotide pool. Finally, while some AID-GFP fused molecules localized to nucleoids, and a significant portion appears to be distributed throughout the bacterial cell, the highest concentration seemed to localize to the cell poles. Chloramphenicol treatment, which detaches the nucleoids from the membrane, caused a further disassociation of AID-GFP from nucleoids suggesting that AID does not intrinsically bind DNA. These results strongly argue against a role for AID in mutagenesis by deamination of cytosine in the nucleotide pool, and suggest that while AID probably acts by deaminating cytosine in the DNA, it requires a protein partner for efficient localization to DNA.

Structural analysis, selection, and ontogeny of the shark new antigen receptor (IgNAR): identification of a new locus preferentially expressed in early development.

The new antigen receptor (IgNAR) family has been detected in all elasmobranch species so far studied and has several intriguing structural and functional features. IgNAR protein, found in both transmembrane and secretory forms, is a dimer of heavy chains with no associated light chains, with each chain of the dimer having a single free and flexible V region. Four rearrangement events (among 1V, 3D, and 1J germline genes) generate an expressed NAR V gene, resulting in long and diverse CDR3 regions that contain cysteine residues. IgNAR mutation frequency is very high and "selected" mutations are found only in genes encoding the secreted form, suggesting that the primary repertoire is entirely CDR3-based. Here we further analyzed the two IgNAR types, "type 1" having one cysteine in CDR3 and "type 2" with an even number (two or four) of CDR3 cysteines, and discovered that placement of the disulfide bridges in the IgNAR V domain differentially influences the selection of mutations in CDR1 and CDR2. Ontogenetic analyses showed that IgNAR sequences from young animals were infrequently mutated, consistent with the paradigm that the shark immune system must become mature before high levels of mutation accompanied with selection can occur. Nevertheless, also in agreement with the idea that the IgNAR repertoire is entirely CDR3-based, but unlike studies in most other vertebrates, N-region diversity is present in expressed IgNAR clones at birth. During the investigation of this early IgNAR repertoire we serendipitously detected a third type of IgNAR gene that is expressed in all neonatal tissues; later in life its expression is perpetuated only in the epigonal organ, a tissue recently shown to be a (the?) primary lymphoid tissue in elasmobranchs. This "type 3" IgNAR gene still undergoes three rearrangement events (two D regions are "germline-joined"), yet CDR3 sequences were exactly of the same length and very similar sequence, suggesting that "type 3" CDR3s are selected early in ontogeny, perhaps by a self-ligand.

Conjuntivite viral epidêmica em pacientes geriátricos: tratamento homeopático / Epidemic viral conjunctivitis in geriatric patients: homeopathic treatment

40 pacientes geriátricos com conjuntivite viral aguda epidêmica, foram atendidos no Lar de Idosos Hermanas Giral (Cienfuegos) e divididos em 2 grupos. As variáveis analisadas foram tempo de desaparecimento e de melhoria dos sintomas ardor, secreçäo e congestäo. O grupo A recebeu tratamento com Pulsatilla 6CH via oral e Euphrasia em fomentos oculares. O grupo B recebeu Leuferon colírio e fomentos de água fervida. O presente estudo mostra resultados promissores para a terapia homeopática.