Continued RAG expression in late stages of B cell development and no apparent re-induction after immunization

Models of B-cell development in the immune system suggest that only those immature B cells in the bone marrow that undergo receptor editing express V(D)J-recombination-activating genes (RAGs). Here we investigate the regulation of RAG expression in transgenic mice carrying a bacterial artificial chromosome that encodes a green fluorescent protein reporter instead of RAG2. We find that the reporter is expressed in all immature B cells in the bone marrow and spleen. Endogenous RAG messenger RNA is expressed in immature B cells in bone marrow and spleen and decreases by two orders of magnitude as they acquire higher levels of surface immunoglobulin M (IgM). Once RAG expression is stopped it is not re-induced during immune responses. Our findings may help to reconcile a series of apparently contradictory observations, and suggest a new model for the mechanisms that regulate allelic exclusion, receptor editing and tolerance.

Structure and physical map of 64 variable segments in the 3'0.8-megabase region of the human immunoglobulin heavy-chain locus

We have constructed the physical map of the 0.8 megabase DNA fragment which contains the 3' 64 variable region (V) gene segments of the human immunoglobulin heavy chain (H) locus. The organization of the VH locus showed several features that indicate dynamic reshuffling of this locus. The sequenced 64 VH segments include 31 pseudogenes, of which 24 are highly conserved except for a few point mutations. Comparison of the 64 germline VH sequences shows that each VH family has conserved sequences, suggesting that there might be some genetic or selection mechanisms involved in maintenance of each family. The total number of the human VH segments was estimated to be about 120, including at least 7 orphons.

Detection of Norwalk-like virus genes in the caecum contents of pigs

Norwalk-like virus genes were detected by RT-PCR in the caecum contents of pigs. Positive PCR products were produced from four out of 1,117 samples by nested PCR using human SRSV primers. Nucleotide sequences between 4,561 and 4,852 numbered according to the Norwalk virus genomic RNA in the RNA polymerase region were determined. Between the Norwalk virus sequence and the sequences detected in pigs, there was 58.2% to 59.9% sequence homology. The swine sequences were located on genogroup II of human SRSVs, but formed a subgroup in the phylogenetic tree of caliciviruses.

Tumor necrosis factor receptor-associated factor 6 (TRAF6) stimulates extracellular signal-regulated kinase (ERK) activity in CD40 signaling along a ras-independent pathway

CD40 activates nuclear factor kappa B (NF kappa B) and the mitogen-activated protein kinase (MAPK) subfamily, including extracellular signal-regulated kinase (ERK). The CD40 cytoplasmic tail interacts with tumor necrosis factor receptor-associated factor (TRAF)2, TRAF3, TRAF5, and TRAF6. These TRAF proteins, with the exception of TRAF3, are required for NF kappa B activation. Here we report that transient expression of TRAF6 stimulated both ERK and NF kappa B activity in the 293 cell line. Coexpression of the dominant-negative H-Ras did not affect TRAF6-mediated ERK activity, suggesting that TRAF6 may activate ERK along a Ras-independent pathway. The deletion mutant of TRAF6 lacking the NH2-terminal domain acted as a dominant-negative mutant to suppress ERK activation by full-length CD40 and suppress prominently ERK activation by a deletion mutant of CD40 only containing the binding site for TRAF6 in the cytoplasmic tail (CD40 delta 246). Transient expression of the dominant-negative H-Ras significantly suppressed ERK activation by full-length CD40, but marginally suppressed ERK activation by CD40 delta 246, compatible with the possibility that TRAF6 is a major transducer of ERK activation by CD40 delta 246, whose activity is mediated by a Ras-independent pathway. These results suggest that CD40 activates ERK by both a Ras-dependent pathway and a Ras-independent pathway in which TRAF6 could be involved.

Physical map of the 3′ region of the human immunoglobulin heavy chain locus: clustering of autoantibody-related variable segments in one haplotype

We have constructed the physical map of the 3' region of the human immunoglobulin heavy chain variable region (VH) genes. DNA segments extending to 200 kb upstream of the JH segment were isolated in two YAC clones. Five VH segments were identified in this region in the 5' to 3' order, V(II-5), V(IV-4), V(I-3), V(I-2), and V(VI-1) segments which were all structurally normal and orientated in the same direction as the JH segments. From DNA of a different cell line we have isolated a cosmid contig containing the same DNA region which has extraordinary polymorphism. The YAC and cosmid DNAs were called haplotypes A and B, respectively. Haplotype B contained an additional VH-I segment (V(I-4.1b)) between the V(II-5) and V(IV-4) segments. V(I-4.1b) segment is almost identical to a previously published VH sequence encoding a rheumatoid factor. Another VH segment in the B haplotype (V(I-3b)) corresponding to the V(I-3) segment also showed 99.7% nucleotide sequence homology with an anti-DNA autoantibody VH sequence. However, none of the VH sequences in haplotype A showed such strong homology with autoantibody VH sequences. The results suggest that VH haplotypes may have linkage with autoantibody production.

Organization of variable region segments of the human immunoglobulin heavy chain: duplication of the D5 cluster within the locus and interchromosomal translocation of variable region segments

We have studied the organization of variable region (V) genes of the human immunoglobulin heavy chain (H) by cosmid cloning. We isolated two independent immunoglobulin D5 clusters (D5-a and D5-b) from cosmid libraries of the human genome. Restriction maps of these two regions showed that downstream 15 kb portions of the 55 kb overlap were different although upstream 40 kb portions were almost identical. Four more D segments, (DM, DXP, DA and DK) were found around the D5 segment in the conserved region of each cluster. Nucleotide sequences of the corresponding D segments from each cluster were almost identical and they encoded potentially functional D regions. Analysis using human-rodent somatic cell hybrids demonstrated that both clusters were located in the immunoglobulin heavy chain (H) locus on chromosome 14, suggesting that the D5-a and D5-b regions evolved by internal duplication within this locus. We also isolated a 60 kb DNA region carrying four VH segments, designated as VH-F region, which was located on chromosome 16. Nucleotide sequences of the four VH segments were determined. Two of them encoded potentially functional VH segments, and the other two were pseudogenes. Some more VH segments were found to be located outside chromosome 14, by Southern blot hybridization of human-rodent hybrid cell DNAs. These results provide further evidence that the human VH locus has undergone recent reorganization.

Adduct formation at C-8 of guanine on in vitro reaction of the ultimate form of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine with 2'-deoxyguanosine and its phosphate esters

We examined the reactivity of the N-hydroxyamino derivative of a carcinogenic heterocyclic amine, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), after its O-acetylation with four 2'-deoxyribonucleoside 3'-monophosphates. 32P-Postlabeling analysis demonstrated that the levels of adducts with 2'-deoxyguanosine 3'-monophosphate were much higher than those with the other three nucleotides. 1H-NMR, mass spectral and UV absorption spectral analyses of the major adducts formed by N-acetyoxy-PhIP with 2'-deoxyguanosine and with its phosphate esters indicated that PhIP bound at the C-8 position of guanine, as previously demonstrated with other heterocyclic amines.

Myocardial contractile reserve as prognostic determinant in patients with idiopathic dilated cardiomyopathy without overt heart failure

To assess the prognostic significance of myocardial contractile reserve in patients with idiopathic dilated cardiomyopathy (DCM) without overt heart failure (New York Heart Association functional class I or II), seventy-one patients underwent exercise radionuclide angiography in addition to clinical, radiographic, hemodynamic, and echocardiographic evaluations. Myocardial contractile reserve was assessed as left ventricular ejection fraction (LVEF) during peak exercise minus LVEF at rest (delta LVEF). During an average of 49 months, 18 patients died of the disease. Cox's proportional-hazards regression analysis showed that the delta LVEF was the most powerful and independent discriminator for survival (p = 0.0002). Ejection time (p = 0.0029) and cardiothoracic ratio (p = 0.017) were the second and third most predictive variables, respectively. Evaluation of the delta LVEF, which reflects residual myocardial contractile reserve, can provide important information about the prognosis of patients with DCM and mild symptoms.

Regulation of RAG expression in developing lymphocytes

Proper expression of products of the recombination-activating genes (RAGs) is essential for the development of the adaptive immune system. A major advance in the past year toward understanding RAG regulation is the establishment of green fluorescent protein (GFP)-RAG indicator mouse strains. In vivo visualization of RAG expression in single cells has helped to define the cells that express RAGs in secondary lymphoid organs and revealed differential cis requirements for stage- and lineage-specific RAG expression.

Trichosporon beigelii pneumonia in patients with hematologic malignancies

Trichosporon beigelii is a causative agent of hypersensitivity pneumonia in immunocompetent individuals and of invasive pneumonia in immunocompromised patients. The actual incidence and clinical manifestations of T beigelii pneumonia are obscure because the diagnosis is sometimes difficult. We studied eight patients with T beigelii pneumonia diagnosed by immunohistochemical investigation of lung tissue sections and/or isolation of the organism from the lung, sputum, or blood. All patients had underlying hematologic malignancies for which they had received cytotoxic chemotherapy, resulting in profound neutropenia. The clinical manifestations were persistent fever unresponsive to broad-spectrum antibiotic therapy, cough, bloody sputum, and rapidly progressive dyspnea. The chest radiographs showed diffuse alveolar infiltrates in four patients, diffuse interstitial infiltrates in one, patchy reticulonodular infiltrates in one, and focal alveolar infiltrates in two. Histopathologic examination demonstrated numerous centrally necrotic foci with minimal cellular inflammatory reaction, intra-alveolar hemorrhage, and edema. Trichosporon beigelii consisting of both yeast and hyphal forms was located predominantly in the alveolar vessels. In neutropenic patients with hematologic malignancies, this fungus appears to enter the lung not only through the airways but also via the hematogenous route. In vitro susceptibility testing indicated borderline susceptibility to amphotericin B and showed that some azoles were active against T beigelii at safely achievable serum concentrations.

Analysis of a vinyl pyrrolidone/poly(propylene fumarate) resorbable bone cement

A resorbable bone cement was formulated from N-vinyl-2-pyrrolidinone (VP), the unsaturated polyester poly(propylene fumarate) (PPF), and the inorganic filler tribasic calcium phosphate (hydroxy apatite). Cure, initiated by benzoyl peroxide and accelerated by N,N-dimethyl-p-toluidine, resulted in the formation of VP crosslinks between polyester chains. During cure the cement hardened from a viscous moldable putty to a rigid structure with a shore D hardness of 50-60. The purpose of this study was to determine the fractions of PPF and VP incorporated into the crosslinked structure. Dissolution of the cured cement in water followed by extraction of the residue in tetrahydrofuran indicated that over 90% of the PPF was crosslinked over the range of PPF/VP ratios explored, but that the fraction of VP used in formation of crosslinks depended linearly on the PPF/VP ratio. Kinetic analysis of these data suggests that k'pp/kpf (the reactivity ratio) was approximately 2.0 where k'pp is the rate constant for the addition of VP radical to VP monomer leading to formation of poly(vinyl pyrrolidone), and kpf is for the addition of VP radical to PPF unsaturation.

Identification of N2-(deoxyguanosin-8-yl)-2-amino-3,8-dimethyl-imidazo[4,5- f]quinoxaline 3',5'-diphosphate, a major DNA adduct, detected by nuclease P1 modification of the 32P-postlabeling method, in the liver of rats fed MeIQx

The carcinogenic heterocyclic amine 2-amino-3,8-dimethyl-imidazo[4,5-f]quinoxaline (MeIQx) is widely distributed in cooked foods. The nuclease P1 method increased the sensitivity of the standard 32P-postlabeling analysis about 1000-fold for detection of MeIQx-DNA adducts. The recovery of MeIQx-DNA adducts by the nuclease P1 method was determined to be about 50% using liver DNA of a rat treated with [14C]MeIQx intragastrically. By the nuclease P1 method five adducts were detected in the liver DNA of rats fed MeIQx and two of them, including the most abundant one, were identified as MeIQx-deoxyguanosine adducts by comparison with the adducts formed in in vitro reactions of N-acetoxy-2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline with the four 2'-deoxyribonucleotides. The most abundant adduct in vivo was identified as N2-(deoxyguanosin-8-yl)-MeIQx 3',5'-diphosphate (3',5'-pdGp-C8-MeIQx). MeIQx-DNA adduct levels in human tissues could be determined by the nuclease P1 modification of the 32P-postlabeling method in combination with HPLC, and thus provide information on the roles of MeIQx in human carcinogenesis.

Role of glycosaminoglycans of biglycan in BMP-2 signaling

Recently we have reported that biglycan (BGN) promotes osteoblast differentiation and that this function is due in part to its ability to positively modulate bone morphogenetic protein (BMP) functions. In this study we investigated the role of glycosaminoglycans (GAGs) of BGN in this function using in vitro and in vivo models. C2C12 myogenic cells were treated or untreated with BMP-2 alone or in combination with glycanated, partially glycanated or de-glycanated BGN, and the effects on BMP signaling and function were assessed by Smad1/5/8 phosphorylation and alkaline phosphatase (ALP) activity. Furthermore, the effect of de-glycanation of BGN on BMP-2 induced osteogenesis was investigated employing a rat mandible defect model. The defects were filled with collagen scaffolds loaded with glycanated or de-glycanated BGN alone or in combination with a sub-optimal dose of BMP-2 (subBMP). In in vitro experiments, BMP signaling and function were the greatest when BMP-2 was combined with de-glycanated BGN among the groups tested. In the rat mandible experiments, μCT analyses revealed that the newly formed bone was significantly increased only when subBMP was combined with de-glycanated BGN. The data indicate that the GAG component of BGN functions as a suppressor for the BGN-assisted BMP function.

Inhibition of kinin formation by a kallikrein inhibitor during extracorporeal circulation in open-heart surgery

Involvement of the kinin system was studied in 58 patients during extracorporeal circulation in open heart surgery. At the onset of extracorporeal circulation, there was no increase of free kinin in blood and no reduction of plasma kininogen, when the latter was expressed as mug bradykinin/mg plasma protein. With the lapse of time, kinin in the blood increased significantly, and decrease of kininogen was also significant. The longer the circulation time, the greater the consumption of kininogen. The site of the kinin formation was presumed to be the heart-lung machine since the level of kinin increased slightly and kininogen decreased gradually in the blood leaving the machine, compared with those levels entering the machine. The difference in kininogen was significantly different from zero at termination of extracorporeal circulation. Administration of a kallikrein-trypsin inhibitor, trasylol (A. G. Bayer), infused into the heart-lung machine, prevented the decrease of kininogen. Reduction of the total peripheral resistance during this circulation was also prevented. The hemoconcentration, presumably the result of vascular permeability increase caused by increased kinin, was prevented by trasylol in cases in which extracorporeal circulation lasted over 60 minutes. Trasylol applied thus appears to be an effective counteragent for circulatory disturbances which occur during extracorporeal circulation.

Isolation of Coxiella burnetii from children with influenza-like symptoms in Japan

The prevalence of Coxiella burnetii antibodies was investigated by indirect immunofluorescence (IF) test in 55 paired sera (acute and convalescent phases) of school children who had influenza-like symptoms. Of the convalescent serum samples examined, 18 (32.7%) sera reacted positively to phase II antigen of C. burnetii. Coxiella-like organism was isolated from the sera of 13 children after injection of the 18 acute phase sera into mice. The organism was identified as C. burnetii by Giemsa staining and the IF antigen test of mouse spleen smears, the polymerase chain reaction (PCR) method, electron microscopic observations of the mouse spleen cells, and the IF antibody test of mouse sera. This is the first report of isolation of C. burnetii from serum specimens of children having influenza-like symptoms. The evidence that C. burnetii was isolated from people indigenous to Japan at a considerably high incidence suggested that C. burnetii may be widespread as a cause of influenza-like symptoms in Japan.

Use of fibrinogen to enhance the antitumor effect of OK-432. A new approach to immunotherapy for colorectal carcinoma

OK-432 (5 KE), an immunomodulatory agent prepared from an attenuated strain of Streptococcus pyogenes, was dissolved in 1 ml of aprotinin (1000 KIE) and mixed with 80 mg of fibrinogen containing Factor XIII. A single intratumoral injection of the mixture was performed preoperatively under endoscopy in 20 patients with colorectal carcinoma. Postoperative histopathologic examinations revealed the formation of fibrin fibers at the site of injection and marked infiltration of inflammatory cells into the tumor stroma on the day after injection; the formation of granulomas containing many giant cells after 4 to 7 days; and extensive regression of tumor tissue after 14 days. This study suggests that the high concentration of exogenous fibrinogen gelatinized enough to trap OK-432 in tumor stroma and that OK-432 induced granulomatous hypersensitivity to degenerate tumor stroma, thereby causing regression of the tumors.

Accumulation of somatic hypermutation and antigen-driven selection in rapidly cycling surface Ig+ germinal center (GC) B cells which occupy GC at a high frequency during the primary anti-hapten response in mice

Well-developed germinal centers (GC) contain rapidly dividing surface immunoglobulin-negative (sIg-) B cells (centroblasts), and most of their progeny are sIg+ B cells (centrocytes) in a resting state. It has been predicted that somatic hypermutation occurs in centroblasts, whereas antigen-driven selection takes place in centrocytes. The present analysis indicates that murine GC B cells bearing sIg with specificity for an immunizing antigen are in a rapidly cycling state and increase exponentially in number to occupy spleen GC at high frequency during the 1st week after primary immunization; however, the number of these cells is significantly reduced in the 2nd week of immunization. During that period, these proliferating sIg+ GC B cells accumulate somatic hypermutations with nucleotide exchanges indicative of affinity maturation. These sIg+ GC B cells co-express B7-2, ICAM-1, and LFA-1, and have potent antigen-presenting activity which results in T cell activation in vitro. These observations indicate that the sIg+ GC B cells accumulate somatic hypermutations and undergo antigen-driven selection through proliferation, probably upon activation by T cells. This sIg+ GC B cell population may represent cell cycling centrocytes; however, the possibility that these may represent centroblasts undergoing re-expression of sIg could not be excluded.

PV1, a novel Plasmodium falciparum merozoite dense granule protein, interacts with exported protein in infected erythrocytes

Upon invasion, Plasmodium falciparum exports hundreds of proteins across its surrounding parasitophorous vacuole membrane (PVM) to remodel the infected erythrocyte. Although this phenomenon is crucial for the parasite growth and virulence, elucidation of precise steps in the export pathway is still required. A translocon protein complex, PTEX, is the only known pathway that mediates passage of exported proteins across the PVM. P. falciparum Parasitophorous Vacuolar protein 1 (PfPV1), a previously reported parasitophorous vacuole (PV) protein, is considered essential for parasite growth. In this study, we characterized PfPV1 as a novel merozoite dense granule protein. Structured illumination microscopy (SIM) analyses demonstrated that PfPV1 partially co-localized with EXP2, suggesting the protein could be a PTEX accessory molecule. Furthermore, PfPV1 and exported protein PTP5 co-immunoprecipitated with anti-PfPV1 antibody. Surface plasmon resonance (SPR) confirmed the proteins’ direct interaction. Additionally, we identified a PfPV1 High-affinity Region (PHR) at the C-terminal side of PTP5 where PfPV1 dominantly bound. SIM analysis demonstrated an export arrest of PTP5ΔPHR, a PTP5 mutant lacking PHR, suggesting PHR is essential for PTP5 export to the infected erythrocyte cytosol. The overall results suggest that PfPV1, a novel dense granule protein, plays an important role in protein export at PV.

Recent translocation of variable and diversity segments of the human immunoglobulin heavy chain from chromosome 14 to chromosomes 15 and 16

We studied the organization and origin of three orphon regions, VH-F, D5-a, and D5-b, of the human immunoglobulin heavy-chain gene using yeast artificial chromosomes. VH-F and two D5 regions were mapped to chromosome bands 16p11 and 15q11-q12, respectively, by using human/rodent somatic cell hybrids and fluorescence in situ hybridization. No D5 segments were found on chromosome 14, in contradiction to previous reports. The VH-F region consists of 7 VH segments and encompasses 160 kb of DNA. A cluster of VH segments homologous to the VH-F region orphons was found in the region 245-430 kb (V2-26 to V3-11) upstream of the JH cluster on chromosome 14. Comparison of VH sequences between the VH-F and the chromosome 14 loci indicates that the translocation of the VH-F region took place, at the earliest, 20 x 10(6) years ago. The D5-a and D5-b regions were obtained in two independent contigs. The former contains only D segments in 140 kb of DNA, while the latter carries 3 VH segments downstream of D segments in 110 kb of DNA. V54, one of these VH orphon segments, is about 95% homologous to V1-18, which is located within the putative ancestor of the VH-F region on chromosome 14. Furthermore, the region detected by two DNA probes flanking the V54 segment was found only in the proximity of V1-18 within the 0.8-Mb VH region on chromosome 14. These results suggest that the two orphon loci on chromosomes 15 and 16 may have been translocated simultaneously.

Preservation of pancreatic beta cell function with pulsatile cardiopulmonary bypass

Pancreatic islet cell function and tissue metabolism were studied during and after cardiopulmonary bypass in 38 patients undergoing an open heart operation. Twenty patients were operated on with pulsatile cardiopulmonary bypass (group I) and 18, with nonpulsatile cardiopulmonary bypass (group II). Hyperglycemia was observed during and early after operation in both groups. In group I during cardiopulmonary bypass, the immunoreactive insulin and c-peptide levels and the insulin to glucagon molar ratio increased significantly compared with the preoperative values, but in group II, these variables did not alter significantly. An hour postoperatively, the immunoreactive insulin (71 +/- 34 muIU/mL) and c-peptide (8.3 +/- 3.0 ng/mL) levels and the insulin to glucagon molar ratio (11.0 +/- 5.2) in group I were significantly higher than those in group II (immunoreactive insulin, 29 +/- 20 muIU/mL; c-peptide, 4.8 +/- 1.8 ng/mL; insulin to glucagon molar ratio, 3.4 +/- 2.6). The blood lactate level in group I (41 +/- 22 mg/dL) was significantly lower than that in group II (78 +/- 30 mg/dL) an hour postoperatively. In conclusion, pulsatile cardiopulmonary bypass is quite effective in preserving pancreatic beta cell function and tissue metabolism during and early after open heart procedures.