Fc galactosylation of anti-platelet human IgG1 alloantibodies enhances complement activation on platelets

Approximately 20% of patients receiving multiple platelet transfusions develop platelet alloantibodies, which can be directed against human leukocyte antigens (HLA) and, to a lesser extent, against human platelet antigens (HPA). These antibodies can lead to the rapid clearance of donor platelets, presumably through IgG-Fc receptor (FcγR)-mediated phagocytosis or via complement activation, resulting in platelet refractoriness. Strikingly, not all patients with anti-HLA or -HPA antibodies develop platelet refractoriness upon unmatched platelet transfusions. Previously, we found that IgG Fc glycosylation of anti-HLA antibodies was highly variable between patients with platelet refractoriness, especially with respect to galactosylation and sialylation of the Fc-bound sugar moiety. Here, we produced recombinant glycoengineered anti-HLA and anti- HPA-1a monoclonal antibodies with varying Fc galactosylation and sialylation levels and studied their ability to activate the classical complement pathway. We observed that anti-HLA monoclonal antibodies with different specificities, binding simultaneously to the same HLA-molecules, or anti-HLA in combination with anti-HPA-1a monoclonal antibodies interacted synergistically with C1q, the first component of the classical pathway. Elevated Fc galactosylation and, to a lesser extent, sialylation significantly increased the complement-activating properties of anti-HLA and anti-HPA-1a monoclonal antibodies. We propose that both the breadth of the polyclonal immune response, with recognition of different HLA epitopes and in some cases HPA antigens, and the type of Fc glycosylation can provide an optimal stoichiometry for C1q binding and subsequent complement activation. These factors can shift the effect of a platelet alloimmune response to a clinically relevant response, leading to complement-mediated clearance of donor platelets, as observed in platelet refractoriness

Analysis of Mycobacterium tuberculosis-Specific CD8 T-Cells in Patients with Active Tuberculosis and in Individuals with Latent Infection

CD8 T-cells contribute to control of Mycobacterium tuberculosis infection, but little is known about the quality of the CD8 T-cell response in subjects with latent infection and in patients with active tuberculosis disease. CD8 T-cells recognizing epitopes from 6 different proteins of Mycobacterium tuberculosis were detected by tetramer staining. Intracellular cytokines staining for specific production of IFN-γ and IL-2 was performed, complemented by phenotyping of memory markers on antigen-specific CD8 T-cells. The ex-vivo frequencies of tetramer-specific CD8 T-cells in tuberculous patients before therapy were lower than in subjects with latent infection, but increased at four months after therapy to comparable percentages detected in subjects with latent infection. The majority of CD8 T-cells from subjects with latent infection expressed a terminally-differentiated phenotype (CD45RA+CCR7−). In contrast, tuberculous patients had only 35% of antigen-specific CD8 T-cells expressing this phenotype, while containing higher proportions of cells with an effector memory- and a central memory-like phenotype, and which did not change significantly after therapy. CD8 T-cells from subjects with latent infection showed a codominance of IL-2+/IFN-γ+ and IL-2−/IFN-γ+ T-cell populations; interestingly, only the IL-2+/IFN-γ+ population was reduced or absent in tuberculous patients, highly suggestive of a restricted functional profile of Mycobacterium tuberculosis-specific CD8 T-cells during active disease. These results suggest distinct Mycobacterium tuberculosis specific CD8 T-cell phenotypic and functional signatures between subjects which control infection (subjects with latent infection) and those who do not (patients with active disease)

Afucosylated IgG characterizes enveloped viral responses and correlates with COVID-19 severity

Immunoglobulin G (IgG) antibodies are crucial for protection against invading pathogens. A highly conserved N-linked glycan within the IgG-Fc tail, which is essential for IgG function, shows variable composition in humans. Afucosylated IgG variants are already used in anticancer therapeutic antibodies for their increased activity through Fc receptors (Fc gamma RIIIa). Here, we report that afucosylated IgG (approximately 6% of total IgG in humans) are specifically formed against enveloped viruses but generally not against other antigens. This mediates stronger Fc gamma RIIIa responses but also amplifies brewing cytokine storms and immune-mediated pathologies. Critically ill COVID-19 patients, but not those with mild symptoms, had high concentrations of afucosylated IgG antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), amplifying proinflammatory cytokine release and acute phase responses. Thus, antibody glycosylation plays a critical role in immune responses to enveloped viruses, including COVID-19.Proteomic

Studies in wave digital filter theory and design

Electrical Engineering, Mathematics and Computer Scienc

N. Dumitru, R. Nouta

This paper presents a model for characterizing delay for CMOS logic cells that accounts for input slope and output capacitance loading. The method yields almost Spice-like accuracy, and allows accurate delay simulations to be carried out at VHDL simulation speed. The errors of the VHDL model are less than 5% of Spice results. 1 Introduction In this paper we present a CMOS cell delay model which accounts for both input slope and output load in deriving the delay values. Our modeling approach is based on piece-wise linear fitting of the model parameters to a number of Spice3 simulations. The model parameters for each cell are derived from circuit simulations of the netlist based on cell's layout using lateral interconnect capacitance. Level-3 transistor modeling is used. We have determined the delay parameters for our Sea-of-Gates 1 (SoG) library cells, such as: buffer, inverter, nand2, nor2, exclusive-or, edge triggered D flip-flop, edge triggered D flip-flop with synchronous reset. ..

VHDL Power estimation of CMOS Logic Cells

This paper presents an improved VHDL implementation of a power- and delay model which accounts for input slope, output capacitive loading and glitches. The model parameters are based on a piece-wise linear fitting of the parameters to a number of Spice simulations for both the delay and power models. Results from VHDL simulations typically lie within 10% of the Spice results. Keywords--- VHDL, power estimation, Sea of Gates, CMOS, Spice. I. Introduction In this paper we present an improved CMOS power model which accounts for signal slope and output load in deriving the power values. A VHDL power and delay model was developed by Dumitru [1] which showed that Spice accuracy can be achieved at VHDL simulation speeds. This model has been used as a basis for further improvements. A number of problems with Dumitru's approach have been solved and the accuracy of the model for larger circuits has been improved. This paper is structured as follows: Section II presents a detailed overview of t..

Comparison of the Dynamic Behavior of Different Multipliers in the 8 × 8 Inverse Discrete Cosine Transform, using VHDL

The Inverse Discrete Cosine Transform (idct) is used in almost all video-decoders, like mpeg and hdtv. In de process of video decoding, the idct is a computationally heavy part. One of the performance characteristics is the power consumption, which is related to the dynamic behavior of the hardware. In this paper the signal transitions that occur in the multipliers are analyzed with vhdl, when two's complement arithmetic is changed in signed binary arithmetic. The simulations show that the signed binary multipliers need about three time less signal transitions than two's complement multipliers. I. Introduction The use of digital coded video signals (images) will increase in the near future. Digital signals are more robust and more flexible then the analogue representations. On the other hand digital video needs a lot of data (ca. 200 Mbit/sec). Therefore compression of the images, and the image-sequences is necessary. The current standard for coding digital image-sequences is mpeg, ..