Role of BCR affinity in T cell dependent antibody responses in vivo

Antibody affinity for antigen is believed to govern B lymphocyte selection during T-dependent immune responses. To examine antibody affinity in T cell dependent immune responses, we compared mice that carry targeted V(H)B1-8 antibody genes with high or low antigen-binding affinity. We found that high- and low-affinity B cells had the same intrinsic capacity to respond to antigen, but in experiments where limiting numbers of high- and low-affinity B cells were mixed in wild-type recipient mice, only the high-affinity B cells accumulated in germinal centers (GCs). In GCs, high-affinity B cells accumulated fewer V(H) somatic mutations than low affinity B cells. This effect was due to selections as the frequency of mutation in noncoding immunoglobulin gene DNA is the same in high- and low- affinity B cells. Thus, B cells recruited to the GC appeared to undergo a fixed mutation program, regardless of initial B cell receptor affinity. We conclude that in addition to the selection that occurs in GCs, stringent selection for high-affinity clones is also imposed in the early stages of the T cell dependent immune response in vivo.     

Prostate adenocarcinoma using Gleason scores correlates with prostate-specific antigen and prostate acid phosphatase measurements.

To evaluate a relationship between Gleason scores of histopathology of prostate carcinoma and concurrent serum prostate-specific antigen (PSA) and prostate acid phosphatase (PAP) values, 65 men with prostate carcinoma were studied. These patients' cumulative Gleason scores were obtained by totaling the primary and secondary patterns, resulting in two groups: 42 patients received high (6-10) and 23 received low (2-5) Gleason scores. Serum PSA and PAP values were measured by radioimmunometric assay 1 to 7 days before surgical procedures or biopsy for prostate carcinoma. Mean serum PSA for patients in the high Gleason score group was 134.39 ng/mL (normal range: 0 to 4), and the mean serum PSA for patients in the low Gleason score group was 23.62 ng/mL. Mean serum PAP for patients with high scores was 28.08 ng/mL (normal range: 0 to 5), and the mean serum PAP for patients with low scores was 18.19 ng/mL. Patients with high Gleason scores showed significantly greater elevation of serum PSA than those with low Gleason scores (P = .047), using two samples to test for groups having unequal variants. Prostate acid phosphatase levels of patients with high scores were not significantly higher than the levels in patients with low scores (P = .60). These results indicate that PSA levels but not PAP levels correlate with Gleason scores.     

Serum PSA and PAP measurements discriminating patients with prostate carcinoma from patients with nodular hyperplasia.

Prostatic specific antigen (PSA) and prostatic acid phosphatase (PAP) are the tumor markers for monitoring disease progression or improvement in patients with prostate adenocarcinoma. The clinical utility of PSA and PAP for early detection of prostate adenocarcinoma, however, requires distinction between prostate adenocarcinoma and prostate nodular hyperplasia. The serum PSA and PAP levels were measured in 20 men with histologically proven prostate adenocarcinoma and 28 men with histologically proven prostate nodular hyperplasia. Patients'' blood samples were collected 1 to 7 days prior to the prostate examination, which included a rectal digital examination, transurethral resection, cytoscopy, and prostate biopsy. Sensitivity, specificity, and predictive values of positive and negative results for the discrimination of prostate adenocarcinoma from prostate nodular hyperplasia were 85%, 89%, 85%, and 29%, respectively, for serum PSA (cutoff level: 10 ng/mL) and 40%, 96%, 89%, and 69%, respectively, for serum PAP (cutoff level: 10 ng/mL). Results indicate that marked elevation of serum PSA suggests prostate adenocarcinoma and that serum PSA can discriminate prostate adenocarcinoma from prostate nodular hyperplasia better than serum PAP.     

Serum hepatitis B virus DNA in healthy HBsAg-negative Chinese adults evaluated by polymerase chain reaction

Serum hepatitis B virus (HBV) DNA was assayed using polymerase chain reaction, in 107 HBsAg-negative normal Chinese subjects. The results showed that eight subjects (7.5%) had HBV DNA. In the subgroup with antibody to hepatitis B surface antigen (anti-HBs) and to hepatitis B core antigen (anti-HBc), 7.3% (5/68) were positive for HBV DNA; HBV DNA was not detected in six individuals with anti-HBs only and in nine with anti-HBc only. In four persons with anti-HBc and anti-HBe, one had HBV DNA. In 20 subjects negative for all hepatitis B serological markers, two (10%) were found to have HBV DNA. This study indicates that serological markers are not adequate to rule out HBV infection, and it further implies that present blood donor screening methods may need improving.     

Impact of cadaveric organ donation on Taiwanese donor families during the first 6 months after donation

OBJECTIVE: Organ donation is a complex decision for family members of Asian donors. The impact of cadaveric organ donation on both Chinese and Western donor families has not been well investigated within a cultural framework. The purposes of this study were to follow Chinese family members' appraisal of their decision to donate organs, to explore the possible negative and positive impacts of organ donation on their family life, and to determine what help they expected from healthcare providers during the first 6 months after donation. METHODS: Twenty-two family members (10 men and 12 women) of cadaveric organ donors who signed consent forms at an organ transplant medical center in Taiwan participated in this project and completed in-depth interviews during the sixth month after donation. RESULTS: Participants were 25 to 56 years old (mean = 48.15 +/- 8.31 years). The type of kinship of the participants included the donor's parents, older sister, and spouse. Subjects reported several negative impacts: worry about the donor's afterlife (86%), stress due to controversy among family members over the decision to donate (77%), and stress due to others' devaluation of the donation (45%). Positive impacts reported by the subjects included having a sense of reward for helping others (36%), having an increased appreciation of life (32%), having closer family relationships (23%), and planning to shift life goals to the study of medicine (9%). Subjects expected the transplant team to provide information about organ recipients (73%), to submit the necessary documents so that family members could receive healthcare payments from the insurance company (68%), to help resolve legal proceedings and settlements associated with accidents (64%), and to not overly publicize their decision to donate (64%). CONCLUSIONS: Although all of the subjects reported that organ donation was the right decision, the decision to donate did not protect Taiwanese donor families from negative psychocognitive bereavement. The impacts of organ donation were affected by the subject's social cultural, spiritual, and legal context and the nature of their bereavement.     

Dynamic wedge versus physical wedge: a Monte Carlo study

The purpose of this study is to analyze the characteristics of dynamic wedges (DW) and to compare DW to physical wedges (PW) in terms of their differences in affecting beam spectra, energy fluence, angular distribution, contaminated electrons, and dose distributions. The EGS4/BEAM Monte Carlo codes were used to simulate the exact geometry of a 6 MV beam and to calculate 3-D dose distributions in phantom. The DW was simulated in accordance with the segmented treatment tables (STT). The percentage depth dose curves and beam profiles for PW, DW, and open fields were measured and used to verify the Monte Carlo simulations. The Monte Carlo results were found to agree within 2% with the measurements performed using film and ionizing chambers in a water phantom. The present EGS4 calculation reveals that the effects of a DW on beam spectral and angular distributions, as well as electron contamination, are much less significant than those for a PW. For the 6 MV photon beam, a 45 degrees PW can result in a 30% increase in mean photon energy due to the effect of beam hardening. It can also introduce a 5% dose reduction in the build-up region due to the reduction of contaminated electrons by the PW. Neither this mean-energy increase nor such dose reduction is found for a DW. Compared to a DW, a PW alters the photon-beam spectrum significantly. The dosimetric differences between a DW and a PW are significant and clearly affect the clinical use of these beams. The data presented may be useful for DW commissioning.     

The (α2→8)-Linked Polysialic Acid Capsule and Lipooligosaccharide Structure Both Contribute to the Ability of Serogroup B Neisseria meningitidis To Resist the Bactericidal Activity of Normal Human Serum

The molecular basis for the resistance of serogroup B Neisseria meningitidis to the bactericidal activity of normal human sera (NHS) was examined with a NHS-resistant, invasive serogroup B meningococcal isolate and genetically and structurally defined capsule-, lipooligosaccharide (LOS)-, and sialylation-altered mutants of the wild-type strain. Expression of the (α2→8)-linked polysialic acid serogroup B capsule was essential for meningococcal resistance to NHS. The very NHS-sensitive phenotype of acapsular mutants (99.9 to 100% killed in 10, 25, and 50% NHS) was not rescued by complete LOS sialylation or changes in LOS structure. However, expression of the capsule was necessary but not sufficient for a fully NHS-resistant phenotype. In an encapsulated background, loss of LOS sialylation by interrupting the α2,3 sialyltransferase gene, lst, increased sensitivity to 50% NHS. In contrast, replacement of the lacto-N-neotetraose α-chain (Galβ1-4GlcNAcβ1-3Galβ1-4Glc) with glucose extensions (Glc_N) in a galE mutant resulted in a strain resistant to killing by 50% NHS at all time points. Encapsulated meningococci expressing a Hep₂(GlcNAc)→KDO₂→lipid A LOS without an α-chain demonstrated enhanced sensitivity to 50% NHS (98% killed at 30 min) mediated through the antibody-dependent classical complement pathway. Encapsulated LOS mutants expressing truncated Hep₂→KDO₂→lipid A and KDO₂→lipid A structures were also sensitive to 50% NHS (98 to 100% killed at 30 min) but, unlike the wild-type strain and mutants with larger oligosaccharide structures, they were killed by hypogammaglobulinemic sera. These data indicate that encapsulation is essential but that the LOS structure contributes to the ability of serogroup B N. meningitidis to resist the bactericidal activity of NHS.Serogroup B Neisseria meningitidis (the meningococcus) is an obligate human pathogen and remains a leading cause of fulminant septicemia and meningitis. In addition to sporadic outbreaks, large epidemics of serogroup B meningococcal disease continue to occur in many parts of the world, including South America, the United States Pacific Northwest, Western Europe, and New Zealand (4, 22). After penetrating upper respiratory tract mucosal surfaces, N. meningitidis must survive and multiply in the bloodstream to cause sepsis, meningitis, and other manifestations of invasive meningococcal disease. A major mechanism inhibiting or preventing the multiplication of meningococci in the blood is the complement-mediated bactericidal activity of human sera (17, 39). The importance of this activity in the prevention of systemic meningococcal disease is reinforced by host factors that alter bactericidal activity and increase the risk for development of invasive disease. These factors include the absence of bactericidal antibodies against meningococci (17, 18, 45), deficiencies in the complement cascade (13), and the presence of blocking immunoglobulin A antibodies that inhibit the bactericidal activity of human sera (19). The bactericidal activity of human sera against meningococci is also used as a surrogate marker for assessing meningococcal vaccine efficacy.Meningococci have evolved mechanisms that protect them from the bactericidal activity of human sera. Invasive serogroup B meningococcal strains recovered from blood and cerebrospinal fluid often resist being killed by human sera (48). The molecular basis for resistance has been attributed to the expression by this organism of an (α2→8)-linked polysialic acid capsule and a short-chained lipooligosaccharide (LOS) with terminal sialic acid residues (23, 34, 35). Meningococci isolated from the bloodstream in invasive disease, in contrast to nasopharyngeal isolates, are heavily encapsulated (9) and express the L3,7,9 LOS immunotypes (28). These immunotypes have a lacto-N-neotetraose originating from HepI of the inner core, which may be terminally sialylated (34, 62). However, the experimental data defining the precise contributions of the capsule, LOS sialylation, and LOS structure to the ability of serogroup B meningococci to resist the bactericidal activity of human sera is conflicting (11, 15, 20, 21, 27, 37, 63–65).LOS epitopes are immunogenic in infants and children and induce protective bactericidal antibodies in convalescent sera (10, 12). These bactericidal LOS antibodies appear to be directed at conserved low-molecular-weight LOS epitopes (10, 12). LOS is also a component of new serogroup B outer membrane vesicle (OMV) vaccines and is proposed as a basis for other new meningococcal vaccines (1–3, 50). Although changes in the structure of LOS are known to influence the amount and epitopes of bactericidal and other functional antibodies elicited by OMV vaccines (2), the precise LOS structure(s) to include in these and other LOS-containing meningococcal vaccines is uncertain.To help understand the basis for meningococcal survival following mucosal invasion and to facilitate development of meningococcal vaccines which may contain LOS, we created a series of genetically and structurally defined capsule-, sialylation-, and LOS-altered mutants of the serogroup B meningococcal strain NMB. We used these mutants to study the contributions of the capsule, LOS sialylation, and changes in LOS structure to meningococcal resistance to the bactericidal activity of normal human sera (NHS).     

Hepatitis B virus propagated in a rat hepatoma cell line is infectious in a primate model

The human hepatitis B virus (HBV) produced by a rat hepatoma cell line through transfection with HBV DNA is infectious in the human primate model--chimpanzee. Since hepadnaviruses are known to have an extremely narrow host range, our results support the idea that the host species barrier of HBV infection resides on the penetration/adsorption step rather than any postpenetration intracellular event during the virus life cycle.     

Buoyant density in cesium chloride of the human reoviruslike agent of infantile gastroenteritis by ultracentrifugation,electron microscopy,and complement fixation

The buoyant density in cesium chloride of the human reoviruslike (HRVL) agent of infantile gastroenteritis was studied utilizing electron microscopy and complement fixation (CF) for the detection of reoviruslike particles in fractions of the density gradient. Three virus positive stool filtrates were studied. “Full” reoviruslike particles had a density of 1.35–1.37 g/cm³, whereas “empty” particles had a density of 1.29 g/cm³. Peak CF activity coincided with the peak fraction of both the “full” and “empty” reoviruslike particles. In addition, by differential centrifugation, CF activity was also associated with the virion and not a “soluble” antigen.     

Profile of autoantibody to basement membrane zone proteins in patients with mucous membrane pemphigoid: long-term follow up and influence of therapy

Mucous membrane pemphigoid (MMP) is an autoimmune mucocutaneous blistering disease characterized by autoantibodies to components within the basement membrane zone. In this study, we report the titers of autoantibodies to antigens in the BMZ, in the sera of 13 patients, treated with intravenous immunoglobulin as monotherapy over a consecutive 18-month period. Using bovine gingiva lysate as substrate in an immunoblot assay, autoantibodies to human bullous pemphigoid antigens (BPAg1 and BPAg2), human beta4 integrin, and laminin 5 were measured. A statistically significant (P < 0.05) decline in the autoantibody titers to beta4-integrin was observed after 3.42 months of initiating the IVIg therapy. These titers were undetectable after 13 months of therapy. The titers of antibodies to BPAg1 and BPAg2 did not correlate with disease activity or response to therapy. Antibodies to laminins were not detected. In patients with MMP, autoantibody titers to beta4-integrin correlate with disease activity and response to therapy.