925 resultados para HLA B antigen


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BACKGROUND: Blocking leukocyte function-associated antigen (LFA)-1 in organ transplant recipients prolongs allograft survival. However, the precise mechanisms underlying the therapeutic potential of LFA-1 blockade in preventing chronic rejection are not fully elucidated. Cardiac allograft vasculopathy (CAV) is the preeminent cause of late cardiac allograft failure characterized histologically by concentric intimal hyperplasia. METHODS: Anti-LFA-1 monoclonal antibody was used in a multiple minor antigen-mismatched, BALB.B (H-2B) to C57BL/6 (H-2B), cardiac allograft model. Endogenous donor-specific CD8 T cells were tracked down using major histocompatibility complex multimers against the immunodominant H4, H7, H13, H28, and H60 minor Ags. RESULTS: The LFA-1 blockade prevented acute rejection and preserved palpable beating quality with reduced CD8 T-cell graft infiltration. Interestingly, less CD8 T cell infiltration was secondary to reduction of T-cell expansion rather than less trafficking. The LFA-1 blockade significantly suppressed the clonal expansion of minor histocompatibility antigen-specific CD8 T cells during the expansion and contraction phase. The CAV development was evaluated with morphometric analysis at postoperation day 100. The LFA-1 blockade profoundly attenuated neointimal hyperplasia (61.6 vs 23.8%; P < 0.05), CAV-affected vessel number (55.3 vs 15.9%; P < 0.05), and myocardial fibrosis (grade 3.29 vs 1.8; P < 0.05). Finally, short-term LFA-1 blockade promoted long-term donor-specific regulation, which resulted in attenuated transplant arteriosclerosis. CONCLUSIONS: Taken together, LFA-1 blockade inhibits initial endogenous alloreactive T-cell expansion and induces more regulation. Such a mechanism supports a pulse tolerance induction strategy with anti-LFA-1 rather than long-term treatment.

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Type II alveolar epithelial cells (AECII) are well known for their role in the innate immune system. More recently, it was proposed that they could play a role in the antigen presentation to T lymphocytes but contradictory results have been published both concerning their surface expressed molecules and the T lymphocyte responses in mixed lymphocyte cultures. The use of either AECII cell line or fresh cells could explain the observed discrepancies. Thus, this study aimed at defining the most relevant model of accessory antigen presenting cells by carefully comparing the two models for their expression of surface molecules necessary for efficient antigen presentation.

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Intratumoral B lymphocytes are an integral part of the lung tumor microenvironment. Interrogation of the antibodies they express may improve our understanding of the host response to cancer and could be useful in elucidating novel molecular targets. We used two strategies to explore the repertoire of intratumoral B cell antibodies. First, we cloned VH and VL genes from single intratumoral B lymphocytes isolated from one lung tumor, expressed the genes as recombinant mAbs, and used the mAbs to identify the cognate tumor antigens. The Igs derived from intratumoral B cells demonstrated class switching, with a mean VH mutation frequency of 4%. Although there was no evidence for clonal expansion, these data are consistent with antigen-driven somatic hypermutation. Individual recombinant antibodies were polyreactive, although one clone demonstrated preferential immunoreactivity with tropomyosin 4 (TPM4). We found that higher levels of TPM4 antibodies were more common in cancer patients, but measurement of TPM4 antibody levels was not a sensitive test for detecting cancer. Second, in an effort to focus our recombinant antibody expression efforts on those B cells that displayed evidence of clonal expansion driven by antigen stimulation, we performed deep sequencing of the Ig genes of B cells collected from seven different tumors. Deep sequencing demonstrated somatic hypermutation but no dominant clones. These strategies may be useful for the study of B cell antibody expression, although identification of a dominant clone and unique therapeutic targets may require extensive investigation.

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AIM: To evaluate pretreatment hepatitis B virus (HBV) testing, vaccination, and antiviral treatment rates in Veterans Affairs patients receiving anti-CD20 Ab for quality improvement. METHODS: We performed a retrospective cohort study using a national repository of Veterans Health Administration (VHA) electronic health record data. We identified all patients receiving anti-CD20 Ab treatment (2002-2014). We ascertained patient demographics, laboratory results, HBV vaccination status (from vaccination records), pharmacy data, and vital status. The high risk period for HBV reactivation is during anti-CD20 Ab treatment and 12 mo follow up. Therefore, we analyzed those who were followed to death or for at least 12 mo after completing anti-CD20 Ab. Pretreatment serologic tests were used to categorize chronic HBV (hepatitis B surface antigen positive or HBsAg+), past HBV (HBsAg-, hepatitis B core antibody positive or HBcAb+), resolved HBV (HBsAg-, HBcAb+, hepatitis B surface antibody positive or HBsAb+), likely prior vaccination (isolated HBsAb+), HBV negative (HBsAg-, HBcAb-), or unknown. Acute hepatitis B was defined by the appearance of HBsAg+ in the high risk period in patients who were pretreatment HBV negative. We assessed HBV antiviral treatment and the incidence of hepatitis, liver failure, and death during the high risk period. Cumulative hepatitis, liver failure, and death after anti-CD20 Ab initiation were compared by HBV disease categories and differences compared using the χ(2) test. Mean time to hepatitis peak alanine aminotransferase, liver failure, and death relative to anti-CD20 Ab administration and follow-up were also compared by HBV disease group. RESULTS: Among 19304 VHA patients who received anti-CD20 Ab, 10224 (53%) had pretreatment HBsAg testing during the study period, with 49% and 43% tested for HBsAg and HBcAb, respectively within 6 mo pretreatment in 2014. Of those tested, 2% (167/10224) had chronic HBV, 4% (326/7903) past HBV, 5% (427/8110) resolved HBV, 8% (628/8110) likely prior HBV vaccination, and 76% (6022/7903) were HBV negative. In those with chronic HBV infection, ≤ 37% received HBV antiviral treatment during the high risk period while 21% to 23% of those with past or resolved HBV, respectively, received HBV antiviral treatment. During and 12 mo after anti-CD20 Ab, the rate of hepatitis was significantly greater in those HBV positive vs negative (P = 0.001). The mortality rate was 35%-40% in chronic or past hepatitis B and 26%-31% in hepatitis B negative. In those pretreatment HBV negative, 16 (0.3%) developed acute hepatitis B of 4947 tested during anti-CD20Ab treatment and follow-up. CONCLUSION: While HBV testing of Veterans has increased prior to anti-CD20 Ab, few HBV+ patients received HBV antivirals, suggesting electronic health record algorithms may enhance health outcomes.

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The resurgence of pertussis suggests the need for greater efforts in understanding the long-lasting protective responses induced by vaccination. In this paper we dissect the persistence of humoral and B-cell memory responses induced by primary vaccination with two different acellular pertussis (aP) vaccines, hexavalent Hexavac(®) vaccine (Hexavac) (Sanofi Pasteur MSD) and Infanrix hexa(®) (Infanrix) (GlaxoSmithKline Biologicals). We evaluated the specific immune responses in the two groups of children, 5 years after primary vaccination by measuring the persistence of IgG and antibody secreting cells (ASC) specific for vaccine antigens. Part of the enrolled children received only primary vaccination, while others had the pre-school boost dose. A similar level of antigen-specific IgG and ASC was found in Infanrix and Hexavac vaccinated children. The mean IgG levels were significantly higher in children that received the pre-school boost as compared with children that did not receive the boost dose. A longer persistence after the pre-school boost of IgG-Pertussis Toxin (PT) and IgG-pertactin levels was observed in Infanrix primed children, but it was not statistically significant. More than 80% of children presented a positive ASC B memory response. Around 50% of children still presented protective IgG-PT levels which are reduced to 36% in no-boosted children. The pre-school booster dose restores the percentage of protected children above 50%. In conclusion our data underline the importance of giving a booster dose 5 years after primary vaccination and suggest the need for a new vaccine able to induce a long lasting protective response.

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Helicobacter pylori is a human pathogen that colonizes about 50% of the world's population, causing chronic gastritis, duodenal ulcers and even gastric cancer. A steady emergence of multiple antibiotic resistant strains poses an important public health threat and there is an urgent requirement for alternative therapeutics. The blood group antigen-binding adhesin BabA mediates the intimate attachment to the host mucosa and forms a major candidate for novel vaccine and drug development. Here, the recombinant expression and crystallization of a soluble BabA truncation (BabA25-460) corresponding to the predicted extracellular adhesin domain of the protein are reported. X-ray diffraction data for nanobody-stabilized BabA25-460 were collected to 2.25Å resolution from a crystal that belonged to space group P21, with unit-cell parameters a = 50.96, b = 131.41, c = 123.40Å, α = 90.0, β = 94.8, γ = 90.0°, and which was predicted to contain two BabA25-460-nanobody complexes per asymmetric unit.

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Because only 10% of individuals infected with Mycobacterium tuberculosis will eventually develop disease, antigens that are recognized differently by the immune systems of infected healthy and diseased subjects may constitute potential vaccine candidates. Here, the heparin-binding hemagglutinin adhesin (HBHA) is identified as such an antigen. Lymphocytes from 60% of healthy infected individuals (n=25) produced interferon (IFN)-gamma after stimulation with HBHA, compared with only 4% of patients with active tuberculosis (n=24). In the responders, both CD4(+) and CD8(+) cells secreted HBHA-specific IFN-gamma, and the antigen was presented by both major histocompatibility complex class I and II molecules. In contrast to the reduced ability of patients with tuberculosis to produce HBHA-specific IFN-gamma, most of them (82%) produced anti-HBHA antibodies, compared with 36% of the infected healthy subjects. These observations indicate that HBHA is recognized differently by the immune systems of patients with tuberculosis and infected healthy individuals and might provide a marker for protection against tuberculosis.

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A high frequency of Tobacco Mosaic virus (TMV) binding cells was found in spleen cells from unimmunized mice (about 3 to 4%). TMV binding is strongly inhibited by previous incubation with anti immunoglobulin antisera. After stripping of membrane receptors, a full recovery for antigen binding capacity can be observed after 24 hr culture. Experiments are presented to exclude artefactual fluorescent cells: interaction of TMV with some non immunoglobulin membrane components; interaction of fluorescent anti TMV antibody with the Fc receptor of B cells; the binding of TMV to cytophilic immunoglobulins. The occurrence of lymphocytes able to bind several non crossreactive antigens is suggested by three lines of evidence: the high number of antigen binding cells in unimmunized mice, presence of surface immunoglobulins on some TMV binding cells after complete capping of TMV receptors and the direct demonstration of lymphocytes binding TMV and hemocyanin at different membrane sites.

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Polyclonal antibodies were produced to detect the coccidiostat nicarbazin. Due to structural constraints of the active component of nicarbazin, dinitrocarbanilide (DNC), three different compounds that shared a common substructure with DNC were used as antigen mimics. The compounds (N-suceinyl-L-alanyl-L-alanyl-L-alanine 4-nitroanilide (SAN), L-glutamic acid gamma-(p-nitroanilide) (GAN) and p-nitrosuccinanilic acid (NSA)) were conjugated to a carrier protein and used in the immunisation of rabbits. Five different polyclonal sera were produced and consequently characterised. The antibodies exhibited an IC50 range of 2.3-7.6 ng/ml using a competitive ELISA procedure, Serum from one rabbit, R555, exhibited an IC50 of 2.9 ng/ml for DNC and cross-reactivity studies showed that this serum was specific for DNC and did not cross-react with other coccidiostats such as halofuginone, toltrazuril or ronidazole. (C) 2002 Elsevier Science B.V. All rights reserved.

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Skin-draining LN contain several phenotypically distinguishable DC populations, which may be immature or mature. Mature DC are generally considered to have lost the capacity to acquire and present newly encountered Ag. Using antibody-opsonized liposomes as Ag carriers, we show that mature DC purified from skin explants are able to efficiently capture liposomes, process Ag encapsulated within them and activate Ag-specific CD4(+) T cells. Explant DC from mice with Langerhans cells (LC) expressing the primate diphtheria toxin receptor that were exposed to diphtheria toxin in vivo presented Ag as well as explant DC from wild-type mice, indicating that LC are not required and dermal DC are probably responsible for this presentation. We further show that all DC subtypes from LN that capture opsonized Ag are capable of cross-presenting it to CD8(+) T cells. Induction of additional maturation in vivo by LPS or treatment with double-stranded RNA did not alter the Ag presentation capacity of the skin or LN DC subtypes. These results suggest that mature DC present in skin-draining LN may play an important role in the induction of primary and/or secondary immune responses against Ag delivered to the LN that they take up by receptor-mediated endocytosis.

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The regulation of CD4 T cell numbers during an immune response should take account of the amount of antigen (Ag), the initial frequency of Ag-specific T cells, the mix of naive versus experienced cells, and (ideally) the diversity of the repertoire. Here we describe a novel mechanism of T cell regulation that potentially deals with all of these parameters. We found that CD4 T cells establish a negative feedback loop by capturing their cognate MHC/peptide complexes from Ag-presenting cells and presenting them to Ag-experienced CD4 T cells, thereby inhibiting their recruitment into the response while allowing recruitment of naive T cells. The inhibition is Ag specific, begins at day 2 (long before Ag disappearance), and cannot be overcome by providing new Ag-loaded dendritic cells. In this way CD4 T cell proliferation is regulated in a functional relationship to the amount of Ag, while allowing naive T cells to generate repertoire variety.

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In order to provide a better understanding of the interaction between the liver fluke (Fasciola hepatica) and the immune system of its mammalian host immunoreactive ? bacteriophage clones containing F. hepatica cDNA have been isolated. Plasmids from these clones were sequenced and found to encode a family of proteins containing certain common elements. All the clones contained a coding repeating sequence (RRRXCA) which is conserved at the nucleic acid level followed by a non-repeating element coding for the C terminal used by the proteins which shows conservation of amino acids at certain positions. Antisera raised against a ß-galactosidase fusion protein with one of these sequences as a terminal extension was used to localize the immunoreactive antigens. Binding was predominantly in the tegument of the juvenile fluke but was reduced in the adult tegument. The wall of the uterus showed strong reactivity in the adult. Rats immunized with the ß-galactosidase fusion protein showed enhanced resistance to challenge infections. The role of these antigens in the host response to infection by F. hepatica is discussed.