HLA class I expression on human platelets is highly variable and correlates with distinct allele group frequencies.

Background: Human leukocyte antigen (HLA) class I molecules are expressed on platelets and can represent a source of alloimmunization in recipients of platelet transfusions. HLA mismatch between donors and recipients may be associated with the induction of anti-HLA antibodies, which can culminate in refractoriness to platelet transfusions. In the present study we analyzed HLA allele group frequencies and HLA expression levels on human platelets from blood donors.

A phase I, randomized, controlled, dose-ranging study of investigational acellular pertussis (aP) and reduced tetanus-diphtheria-acellular pertussis (TdaP) booster vaccines in adults.

Despite high vaccination coverage worldwide, pertussis has re-emerged in many countries. This randomized, controlled, observer-blind phase I study and extension study in Belgium (March 2012-June 2015) assessed safety and immunogenicity of investigational acellular pertussis vaccines containing genetically detoxified pertussis toxin (PT) (NCT01529645; NCT02382913). 420 healthy adults (average age: 26.

Early Rise of Blood T Follicular Helper Cell Subsets and Baseline Immunity as Predictors of Persisting Late Functional Antibody Responses to Vaccination in Humans.

CD4+ T follicular helper cells (T(FH)) have been identified as the T-cell subset specialized in providing help to B cells for optimal activation and production of high affinity antibody. We recently demonstrated that the expansion of peripheral blood influenza-specific CD4(+)IL-21(+)ICOS1(+) T helper (T(H)) cells, three weeks after vaccination, associated with and predicted the rise of protective neutralizing antibodies to avian H5N1. In this study, healthy adults were vaccinated with plain seasonal trivalent inactivated influenza vaccine (TIIV), MF59(®)-adjuvanted TIIV (ATIIV), or saline placebo.

Ultrastructural Visualization of Vaccine Adjuvant Uptake In Vitro and In Vivo.

Adjuvants are substances that enhance adaptive immune responses when formulated in a vaccine. Alum and MF59 are two vaccine adjuvants licensed for human vaccination. Their mode of action has not been completely elucidated.

Oil-in-Water Emulsion MF59 Increases Germinal Center B Cell Differentiation and Persistence in Response to Vaccination.

Induction of persistent protective immune responses is a key attribute of a successful vaccine formulation. MF59 adjuvant, an oil-in-water emulsion used in human vaccines, is known to induce persistent high-affinity functional Ab titers and memory B cells, but how it really shapes the Ag-specific B cell compartment is poorly documented. In this study, we characterized the Ab- and Ag-specific B cell compartment in wild-type mice immunized with HlaH35L, a Staphylococcus aureus Ag known to induce measurable functional Ab responses, formulated with MF59 or aluminum salts, focusing on germinal centers (GC) in secondary lymphoid organs.

Innate Response Activator (IRA) B Cells Reside in Human Tonsils and Internalize Bacteria In Vitro.

Innate response activator (IRA) B cells have been described in mice as a subset of B-1a B cells that produce granulocyte/macrophage colony-stimulating factor (GM-CSF) and have been found in the spleen upon activation. In humans, identification, tissue localization and functionality of these lymphocytes are poorly understood. We hypothesized that IRA B cells could reside in human palatine tonsils, which are a first line of defense from infection of the upper respiratory tract.

Vaccine adjuvant MF59 promotes retention of unprocessed antigen in lymph node macrophage compartments and follicular dendritic cells.

Ag retention within lymph nodes (LNs) upon vaccination is critical for the development of adaptive immune responses, because it facilitates the encounter of the Ag with cognate lymphocytes. During a secondary exposure of the immune system to an Ag, immune complexes (ICs) that contain the unprocessed Ag are captured by subcapsular sinus macrophages and are transferred onto follicular dendritic cells, where they persist for weeks, facilitating Ag presentation to cognate memory B cells. The impact of adjuvants on Ag retention within the draining LNs is unknown.

Surface molecules on stimulated plasmacytoid dendritic cells are sufficient to cross-activate resting myeloid dendritic cells.

Human plasmacytoid dendritic cells (pDCs) and myeloid dendritic cells (mDCs) are 2 types of antigen-presenting cells that exert complementary roles in innate immune responses. We demonstrated previously that in the presence of suboptimal stimulation or when only 1 dendritic cell type is directly stimulated, contact-dependent crosstalk between mDCs and pDCs leads to the activation of both cell types and thus provides them with the ability to induce an optimal T-cell response. The precise mechanism is currently unknown.

B-cell differentiation in EBV-positive Burkitt lymphoma is impaired at posttranscriptional level by miRNA-altered expression.

Endemic, sporadic and HIV-associated Burkitt lymphoma (BL) all have a B-cell phenotype and a MYC translocation, but a variable association with the Epstein-Barr virus (EBV). However, there is still no satisfactory explanation of how EBV participates in the pathogenesis of BL. A recent investigation suggested that EBV-positive and EBV-negative BL have different cells of origin.