Multiple system atrophy laryngeal stridor treated with radiofrequency-assisted posterior cordotomy and arytenoidectomy

Clinical Autonomic Research -     

Chimerism and tetragametic chimerism in humans: implications in autoimmunity, allorecognition and tolerance

The presence of cells or tissues from two individuals, chimeras, or the presence of cells and tissues that include the gonads, tetragametic chimerism can be detected by the analysis of cytogenetics and analysis of polymorphic genetic markers, using patterns of pedigree inheritance. These methodologies include determination of sex chromosomes, major histocompatibility complex (MHC) polymorphisms and panels of short tandem repeats (STRs) that include mitochondrial DNA markers. Studies routinely involve cases of temporal chimerism in blood transfusion, or following allotransplantation to measure the outcome of the organ, lymphopoietic tissues or bone marrow grafts. Demonstration of persistent chimerism is usually discovered in cases of inter-sexuality due to fusion of fraternal twins or in cases of fusion of embryos with demonstrable allogeneic monoclonality of blood which, excluded maternity or paternity when blood alone is used as the source of DNA. In single pregnancies it is possible to produce two kinds of microchimerism: feto-maternal and materno-fetal, but in cases of fraternal twin pregnancies it is possible to identify three different kinds which are related to cases of vanishing twins that can be identified during pregnancy by imaging procedures; (1) hematopoietic, (2) gonadal, and (3) freemartins when the twins have different sex and the individual born is a female with either gonadal or both gonadal and hematopoietic tissues. Fraternal twin pregnancies can also produce fusion of embryos. Such cases could be of different sex presenting with inter-sexuality or in same sex twins. One of such cases, the best studied, showed evidence of chimerism and tetragametism. In this regard, the case was studied because of disputed maternity of two of her three children. All tissues studied, except for the blood, demonstrated four genetic components but only two in her blood of four possible showed allogeneic monoclonality consistent with the interpretation that her blood originated from one hematopoietic stem cell. Also, microchimerism, due to traffic of cells via materno-fetal or feto-maternal has been prompted by reports of their potential association with the development of autoimmune disorders including systemic lupus erythematosus (SLE) and systemic sclerosis, and in allotransplantation. In addition, their relevance of chimerism in the positive and negative selection of T cells in the thymus has not been addressed. T lymphocytes play a central role in controlling the acquired immune response and furthermore serve as crucial effector cells through antigen specific cytotoxic activity and the production of soluble mediators. Central tolerance is established by the repertoire selection of immature T lymphocytes in the thymus, avoiding the generation of autoreactive T cells. Expression of chimeric antigens in the thymus could modify the generation of specific T cell clones in chimeric subjects and these mechanisms could be important in the induction of central tolerance against foreign antigens important in allo-transplantation. In this review, we discuss the genetics of chimerism and tetragametism and its potential role in thymic selection and the relevance in allotransplantation and autoimmune disorders. This review is dedicated to the memory of Robert A. Good, MD, PhD, an outstanding physician and scientist, one discoverer of the functions of the Thymus in immunobiology and the pioneer of human bone marrow allotransplantation. Presented at the First Robert A Good Society Symposium, St. Petersburg, FL 2006.     

Fluvastatin and atorvastatin affect calcium homeostasis of rat skeletal muscle fibers in vivo and in vitro by impairing the sarcoplasmic reticulum/mitochondria Ca2+-release system

The mechanism by which the 3-hydroxy-3-methyl-glutaryl-CoA reductase inhibitors (statins) induce skeletal muscle injury is still under debate. By using fura-2 cytofluorimetry on intact extensor digitorum longus muscle fibers, here we provided the first evidence that 2 months in vivo chronic treatment of rats with fluvastatin (5 and 20 mg kg-1) and atorvastatin (5 and 10 mg kg-1) caused an alteration of calcium homeostasis. All treated animals showed a significant increase of resting cytosolic calcium [Ca2+]i, up to 60% with the higher fluvastatin dose and up to 20% with the other treatments. The [Ca2+]i rise induced by statin administration was not due to an increase of sarcolemmal permeability to calcium. Furthermore, the treatments reduced caffeine responsiveness. In vitro application of fluvastatin caused changes of [Ca2+]i, resembling the effect obtained after the in vivo administration. Indeed, fluvastatin produced a shift of mechanical threshold for contraction toward negative potentials and an increase of resting [Ca2+]i. By using ruthenium red and cyclosporine A, we determined the sequence of the statin-induced Ca2+ release mechanism. Mitochondria appeared as the cellular structure responsible for the earlier event leading to a subsequent large sarcoplasmic reticulum Ca2+ release. In conclusion, we suggest that calcium homeostasis alteration may be a crucial event for myotoxicity induced by this widely used class of hypolipidemic drugs.     

Migrainous Infarction in a Patient With Sporadic Hemiplegic Migraine and Cystic Fibrosis: A 99mTc-HMPAO Brain SPECT Study

Genetic mutations of sporadic hemiplegic migraine (SHM) are mostly unknown. SHM pathophysiology relies on cortical spreading depression (CSD), which might be responsible for ischemic brain infarction. Cystic fibrosis (CF) is caused by a monogenic mutation of the chlorine transmembrane conductance regulator (CFTR), possibly altering brain excitability. We describe the case of a patient with CF, who had a migrainous stroke during an SHM attack. A 32-year-old Caucasian male was diagnosed with CF, with heterozygotic delta F508/unknown CFTR mutation. The patient experiences bouts of coughing sometimes triggering SHM attacks with visual phosphenes, aphasia, right-sided paresthesia, and hemiparesis. He had a 48-hour hemiparesis triggered by a bout of coughing with hemoptysis, loss of consciousness, and severe hypoxia-hypercapnia. MRI demonstrated transient diffusion hyperintensity in the left frontal-parietal-occipital regions resulting in a permanent infarction in the primary motor area. Later, a brain perfusion SPECT showed persistent diffuse hypoperfusion in the territories involved in diffusion-weighted imaging alteration. Migrainous infarction, depending on the co-occurrence of 2 strictly related phenomena, CSD and hypoxia, appears to be the most plausible explanation. Brain SPECT hypoperfusion suggests a more extensive permanent neuronal loss in territories affected by aura. CF may be then a risk factor for hemiplegic migraine and stroke since bouts of coughing can facilitate brain hypoxia, triggering auras.     

Low-dose recombinant properdin provides substantial protection against Streptococcus pneumoniae and Neisseria meningitidis infection

Modern medicine has established three central antimicrobial therapeutic concepts: vaccination, antibiotics, and, recently, the use of active immunotherapy to enhance the immune response toward specific pathogens. The efficacy of vaccination and antibiotics is limited by the emergence of new pathogen strains and the increased incidence of antibiotic resistance. To date, immunotherapy development has focused mainly on cytokines. Here we report the successful therapeutic application of a complement component, a recombinant form of properdin (P_n), with significantly higher activity than native properdin, which promotes complement activation via the alternative pathway, affording protection against N. menigitidis and S. pneumoniae. In a mouse model of infection, we challenged C57BL/6 WT mice with N. menigitidis B-MC58 6 h after i.p. administration of P_n (100 µg/mouse) or buffer alone. Twelve hours later, all control mice showed clear symptoms of infectious disease while the P_n treated group looked healthy. After 16 hours, all control mice developed sepsis and had to be culled, while only 10% of P_n treated mice presented with sepsis and recoverable levels of live Meningococci. In a parallel experiment, mice were challenged intranasally with a lethal dose of S. pneumoniae D39. Mice that received a single i.p. dose of P_n at the time of infection showed no signs of bacteremia at 12 h postinfection and had prolonged survival times compared with the saline-treated control group (P < 0.0001). Our findings show a significant therapeutic benefit of P_n administration and suggest that its antimicrobial activity could open new avenues for fighting infections caused by multidrug-resistant neisserial or streptococcal strains.Pneumococcal and meningococcal infectious diseases remain a serious threat to public health. Streptococcus pneumoniae is the leading cause of community-acquired pneumonia and a major cause of otitis media, septicemia, and meningitis (1, 2). S. pneumoniae is responsible for ∼1.2 million deaths per year worldwide, with young children and immunocompromised patients at particular risk (3). Neisseria meningitidis causes epidemic bacterial meningitis and septicemia, with high mortality in children and young adults (4). The impact of meningococcal disease on human health is defined by both the risk and the severity of invasive meningococcal infections, with unacceptably high mortality rates, ranging from 10% in patients under optimal clinical therapy with the latest generation of antibiotics to up to 40% in patients with untreated septicemia. Almost one-third of those who survive invasive infections are left with long-term disabilities and long-term morbidity. Globally, the World Health Organization estimates that ∼1.2 million cases of invasive meningococcal infections occur annually, leading to more than 135,000 fatalities (5).Vaccination programs have reduced the rates of infection in developed countries, but neonates and elderly adults remain especially vulnerable (6, 7). The efficacy of vaccination is further limited by the emergence of new strains of S. pneumoniae and N. meningitidis.The complement system plays a major role in the host resistance to both pathogens (8–13). Complement is activated via three routes: the classical pathway, the lectin pathway, and the alternative pathway. Activation of the classical and lectin pathways is mediated by specific recognition molecules. Binding of C1q to the bacterial surface or the Fc region of antibody initiates the classical pathway. The lectin pathway is initiated by carbohydrate recognition molecules, including mannan-binding lectin, ficolins, and collectin 11, which bind directly to bacterial polysaccharides. Activation of the classical or lectin pathway leads to the formation of a C3 convertase (C4b2a), which splits C3 into the biologically active fragments, C3b and C3a. C3b can bind covalently to an activating surface, and hundreds of molecules of C3b can be deposited in close proximity to the C3 convertase complex. Accumulation of C3b close to C4b2a forms the classical pathway C5 convertase C4b2a(3b)_n, in which C4b and C3b form a binding site for C5, orienting it for cleavage by C2a (14, 15).The mechanisms initiating the alternative pathway are less well understood. It is widely accepted that the alternative pathway maintains a continuous state of low-rate activation, which is held in check by potent negative regulators of activation on nonactivating surfaces, such as the surface of host cells. Turnover of the alternative pathway is initiated either by the provision of C3b via the classical pathway, the lectin pathway, or complement-independent proteolysis of C3 or by the spontaneous hydrolysis of C3 to form C3(H₂O). C3b or C3(H₂O) bind factor B to form either the C3bB or C3(H₂O)B zymogen complex. In this complex, factor B is cleaved by factor D, releasing a Ba fragment. The activated C3bBb or C3(H₂O)Bb fragments are themselves C3 convertases, which in turn cleave more C3 into C3a and C3b. Unchecked, the accumulation of C3b rapidly leads to the formation of more alternative pathway convertase complexes, resulting in a physiologically critical positive feedback mechanism—the amplification loop of complement activation (16). The alternative pathway thus amplifies complement activation initiated by any of the three pathways, making it an attractive target for therapeutic intervention designed to modulate complement-mediated immunity and/or inflammatory processes (17).Deposition of C3b and iC3b on the bacterial surface is a key step in the immune response against S. pneumoniae, because complement-mediated opsonisation is essential for clearance of S. pneumoniae through phagocytosis (8). Lysis of bacteria, owing to formation of the membrane attack complex complex, is the critically important biological activity of complement in the defense against N. meningitidis (10). Inherited or acquired deficiencies of the alternative pathway are associated with a high risk of recurrent bacterial infection. Factor B deficiencies significantly increase the risk of S. pneumoniae and Pseudomonas aeruginosa infection (9, 18). In a mouse model of properdin deficiency, the severity of polymicrobial peritonitis was significantly greater in deficient mice compared with their WT littermates (19). Properdin deficiency in humans has been associated with a high risk of meningococcal infections, especially with unusual infective serotypes, such as W-135 and Y (10, 20, 21). In addition, opsonophagocytosis of S. pneumoniae was found to be severely compromised in properdin-deficient sera, and reconstitution of properdin-deficient sera with purified properdin restored the opsonic activity and killing of S. pneumoniae by polymorphonuclear leukocytes (22, 23).Properdin is the only known positive physiological regulator of complement activation. It stabilizes and extends the half-life of the surface-bound C3 convertase C3bBb, and inhibits its degradation by factor I (24–26). In their pioneering 1954 work, Pillemer et al. (26) first described properdin as a serum protein that mediates complement activation and antimicrobial activity in absence of antibodies.Properdin is present in serum at a concentration of ∼5–15 μg/mL (27). Unlike most other complement components, properdin is not synthesized in the liver but rather is expressed by other cells, including monocytes, T cells, mast cells, and granulocytes (19, 28–30). Properdin monomers can assemble into dimers (P₂), trimers (P₃), and tetramers (P₄), formed by head-to-tail association of monomers (each ∼53 kDa) (31, 32). Properdin aggregates, so-called “activated” properdin (P_n), are considered artificial higher-order oligomers formed during the purification of properdin from plasma or during subsequent freeze–thaw cycles (33). The functional activity of properdin increases with the size of the polymers formed (34). By increasing the half-life of the alternative pathway C3 convertase, properdin antagonizes the functional activity of complement factor H, an abundantly expressed plasma component, which promotes inactivation of the alternative pathway C3 convertase and of all C5 convertases of complement by accelerating the decay of these enzyme complexes through binding to complex-bound C3b and by serving as a cofactor in the factor I-mediated conversion of C3b to its inactive form, termed iC3b (35). Interestingly, the two pathogens used in this study were previously shown to express distinct microbial surface components that sequester factor H from host plasma, leading to resistance to the complement-mediated immune clearance of these pathogens (36, 37).In the present study, we addressed the role of the alternative pathway and the effect of administration of recombinant properdin as a tool for boosting alternative pathway activity to augment the immune response against S. pneumoniae or N. meningitidis.