Mutations in activation-induced cytidine deaminase in patients with hyper IgM syndrome

Recent studies have shown that mutations in a newly described RNA editing enzyme, activation-induced cytidine deaminase (AID), can cause an autosomal recessive form of hyper IgM syndrome. To determine the relative frequency of mutations in AID, we evaluated a group of 27 patients with hyper IgM syndrome who did not have defects in CD40 ligand and 23 patients with common variable immunodeficiency. Three different mutations in AID were identified in 18 patients with hyper IgM syndrome, including 14 French Canadians, 2 Lumbee Indians, and a brother and sister from Okinawa. No mutations were found in the remaining 32 patients. In the group of patients with hyper IgM syndrome, the patients with mutations in AID were older at the age of diagnosis, were more likely to have positive isohemagglutinins, and were less likely to have anemia, neutropenia, or thrombocytopenia. Lymphoid hyperplasia was seen in patients with hyper IgM syndrome and normal AID as well as the patients with hyper IgM syndrome and defects in AID.     

Microanatomical study of the arterial blood supply of the facial nerve in the ponto-cerebellar angle

Summary The blood supply of 50 facial nerves was examined during a micro-anatomical study of the ponto-cerebellar angle using injections of colored latex or Chinese ink.The results indicate the presence of a double arterial blood supply: the proximal supply, rising at the level of the brain stem, results from the confluence of three to five arterioles originating from the anterior inferior cerebellar artery or from the basilar artery itself; the distal supply at the level of the internal acoustic meatus arises from the labyrinthine artery.These two arterial systems do not anastomose directly but by way of capillaries of less than 200 microns in diameter.From these findings the authors conclude that certain postoperative facial paralyses, which may arise in spite of the conservation of the nerve, are in fact ischemic in nature.

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Etude micro-anatomique de la vascularisation artérielle du nerf facial dans l'angle ponto-cérébelleux

Résumé Dans le cadre d'une étude micro-anatomique de l'angle ponto-cérébelleux, la vascularisation de 50 nerfs faciaux est examinée sous microscope opératoire après injection au latex coloré ou à l'encre de Chine.Cette étude permet aux auteurs de décrire un double apport artériel: l'un proximal, né au niveau du tronc cérébral, résulte de la confluence de 3 à 5 artérioles issues de l'ACiA ou de l'artère basilaire ellemême; l'autre distal, au niveau du méat acoustique interne, provient de l'artère labyrinthique. Ces deux systèmes artériels ne s'anastomosent pas entre eux à plein canal, mais par des capillaires d'un diamètre inférieur à 200 microns.Les auteurs en tirent argument pour estimer que certaines paralysies faciales post-opératoires survenant malgré la conservation anatomique du nerf, sont de nature ischémique.

     

Klarzelltumor der Lunge

Clear cell tumors of the lung are rare tumors composed of epithelioid HMB45 positive tumor cells. It has been proposed that clear cell tumors generate from perivascular epithelioid cells which are also found in renal angiomyolipoma. Due to its morphologic epithelioid features with clear cytoplasm the distinction from either primary or metastatic clear cell carcinoma is difficult. Usually clinical investigations do not lead to the final diagnosis so that only subsequent histological examination and immunophenotyping can establish the correct tumor classification. We describe the case of a 52 year old woman who underwent exploratory thoracotomy because of a lung mass in the right lower lobe. In frozen sections a solid trabecular tumor was diagnosed, paraffin histology and immunohistochemistry revealed a clear cell tumor of the lung. The difficulty of the correct diagnosis of the clear cell tumor of the lung in frozen sections is discussed as well as the differential diagnosis.     

A unique exonic splice enhancer mutation in a family with X-linked mental retardation and epilepsy points to a novel role of the renin receptor

The renin-angiotensin system (RAS) is essential for blood pressure control and water-electrolyte balance. Until the discovery of the renin receptor, renin was believed to be mainly a circulating enzyme with a unique function, the cleavage of angiotensinogen. We report a unique mutation in the renin receptor gene (ATP6AP2) present in patients with X-linked mental retardation and epilepsy (OMIM no. 300423), but absent in 1200 control X-chromosomes. A silent mutation (c.321C>T, p.D107D) residing in a putative exonic splicing enhancer site resulted in inefficient inclusion of exon 4 in 50% of renin receptor mRNA, as demonstrated by quantitative RT-PCR. Analysis of membrane associated-receptor molecular forms showed the presence of full-length and truncated proteins in the patient. Functional analysis demonstrated that the mutated receptor could bind renin and increase renin catalytic activity, similar to the wild-type receptor, but resulted in a modest and reproducible impairment of ERK1/2 activation. Thus, our findings confirm the importance of the RAS in cognitive processes and indicate a novel specific role for the renin receptor in cognitive functions and brain development.     

Analysis of class switch recombination and somatic hypermutation in patients affected with autosomal dominant hyper-IgM syndrome type 2

Autosomal recessive form of hyper-IgM syndrome type 2 (AR-HIGM2) is secondary to mutations affecting both alleles of AICDA gene encoding activation-induced cytidine deaminase, characterized by defects of immunoglobulin class switch recombination (CSR) and somatic hypermutation (SHM) in most of the patients. We herein report the immunological phenotype of seven patients carrying a single heterozygous R190X mutation in AICDA. Variable defect in in vivo CSR inherited as an autosomal dominant (AD) trait strongly suggests that this heterozygous AICDA mutation causes HIGM (AD-HIGM2). In AD-HIGM2 B cells, CSR was consistently found impaired in vitro. However, in contrast to AR-HIGM2, the CSR-induced double-stranded DNA breaks in the switch region of IgM heavy chain gene were detected. The SHM frequency in V regions of IgM heavy chain gene in B cells was normal in all (but one patient). The characteristics of the AD-HIGM2 phenotype indicate that the AID C-terminal region may be involved in DNA repair machinery required for CSR.     

Modulation of histamine release in the hypothalamus by nitric oxide

Inflammation Research -     

Macrophage response to bacteria: induction of marked secretory and cellular activities by lipoteichoic acids.

Lipoteichoic acids (LTAs) from various bacterial species, including Staphylococcus aureus, Streptococcus pyogenes, Streptococcus pneumoniae, Enterococcus faecalis, and Listeria monocytogenes, were examined for the ability to induce secretory and cellular responses in a pure population of bone marrow-derived mononuclear phagocytes. Some of the highly purified LTAs, in particular LTAs from Bacillus subtilis, S. pyogenes, E. faecalis, and Enterococcus hirae, were able to affect each of the macrophage parameters measured, i.e., reductive capacity, secretion of tumor necrosis factor and nitrite, and tumoricidal activity. As after stimulation with whole organisms or other bacterial products, secretion of tumor necrosis factor induced by these LTAs reached its maximum within the first few hours of the interaction, while secretion of nitrite and tumoricidal activity required 24 to 36 h for full expression. Other purified LTAs, i.e., LTAs from Streptococcus sanguis, S. pneumoniae, and L. monocytogenes, as well as lipomannan from Micrococcus luteus affected only some of these parameters, while native LTA from S. aureus was inactive. There was no obvious correlation between biological activity and chain length, kind of glycosyl substituents, glycolipid structures, or fatty acid composition of LTAs. Deacylation of LTAs resulted in a complete loss of activity, and deacylated LTAs did not impair the activity of their acylated counterparts, suggesting that acyl chains may be essential for binding of LTA to the cell surface. The results demonstrate that some LTA species are potent inducers of macrophage secretory and cellular activities.     

Detection of a novel 40,000 MW excretory Toxoplasma gondii antigen by murine Th1 clone which induces toxoplasmacidal activity when exposed to infected macrophages.

To analyse target molecules of the CD4+ T-cell response to toxoplasma infection, a panel of Toxoplasma gondii-specific murine CD4+ T-cell clones has been established. Clone 3Tx15, belonging to the T helper 1 (Th1) subtype, abolished intracellular parasite growth when co-cultured with macrophages and live toxoplasma at a ratio of 2:2:1. This effect results from macrophage toxoplasmicidal activity induced upon parasite-dependent cellular interaction, an irrelevant Th1 clone failed in this three-party system. Clone 3Tx15 detects its corresponding antigen in the supernatant of infected cells and also reacts with a host cell-free preparation of T. gondii-excreted/secreted antigens. T-cell blot analysis of two-dimensionally separated toxoplasma lysate revealed a molecular weight of about 40,000 for the fractions stimulating clone 3Tx15. As checked in parallel enzyme-linked immunosorbent assay, the 40,000 MW T-cell antigen co-migrates with the excretory protein GRA4, the sole 40,000 MW T. gondii antigen hitherto known to be recognized by T lymphocytes. Nevertheless, neither recombinant GRA4 nor immunoaffinity-purified natural GRA4 was stimulatory for clone 3Tx15. Our findings thus demonstrate that Th1 clone 3Tx15 which induces toxoplasmicidal activity during antigenic interaction with infected macrophages defines a new 40,000 MW excretory T. gondii antigen.     

Ultrastructural study of substance P receptors in the dorsal horn of the rat spinal cord using monoclonal anti-complementary peptide antibody

A monoclonal antibody directed against a peptide (PS5) specified by RNA complementary to the mRNA coding for substance P (SP), was used to label SP receptors in the rat spinal cord as demonstrated by light and electron microscopy. An immunocytochemical method (avidin-biotin-peroxidase) was used on vibratome sections from rats perfused with paraformaldehyde. Immunoreactivity was observed principally in the two superficial layers of the dorsal horn, in lamina X and the region of motoneurons. The labeling was absent when the antibody was preincubated with the complementary peptide (PS5) used as immunogen. Competition between the anti-complementary peptide antibody and different ligands was tested by preincubation of tissue sections with the ligand in the presence of peptidase inhibitors before addition of the antibody. A specific agonist (SP) or antagonist (spantide, RP 67580) at 10⁻⁶M led to total absence of labeling. These results indicate that under our experimental conditions, the anti-complementary peptide antibody recognizes a SP binding site in the rat spinal cord. Electron microscopic study of the two superficial laminae of the dorsal horn showed that immunolabeling was mainly localized extracellularly at apposing neuronal plasma membranes. It was mostly associated with axodendritic or axosomatic appositions. Occasionally labeling was observed between two axon terminals. In all cases, these appositions were non junctional. Generally, neuronal processes involved in these appositions did not contain large granular vesicles. These observations suggest that SP may act in a diffuse, nonsynaptic manner probably on targets distant from SP release sites.     

Metachronous and multiple aneurysmal bone cysts: a rare variant of primary aneurysmal bone cysts

In 1942, Jaffe and Lichtenstein introduced the term aneurysmal bone cyst (ABC). Primary ABC is characterized by the presence of spongy or multi-cameral cystic tissue filled with blood. The process is benign, but it is locally destructive and has a high propensity for recurrence. In this paper, we present the third case of multiple metachronous primary ABCs as a rare variant of ABC. We describe the 10-year history of a 12-year-old boy with metachronous multiple primary ABCs at five different sites (right proximal humerus, right ulna, bilateral distal radius and right lateral clavicle). Furthermore, our patient suffered from vascular malformations, such as aortic isthmus stenosis, hypoplastic thoraco-abdominal aorta and bilateral renal artery stenosis. To date, in contrast to solitary ABC, the multiple lesions have been found more frequently in male individuals. Using interphase cytogenetics, we analyzed three of five of the patients ABCs and one of these was also analyzed by GTG-banding. No chromosomal abnormalities were found. Significantly, we excluded the missense mutation of codon 201 in guanine nucleotide-binding protein 1 gene consistently found in McCune-Albright syndrome (MAS) and in non-MAS cases of polyostotic fibrous dysplasia of bone with or without secondary ABC.