Antibodies, Volume 3, Issue 1 (March 2014) – 10 articles , Pages 1-181

Anti-ferritin autoantibodies are found in many animals. Human ferritin-binding proteins (FBPs) were partially purified from human serum by ion-exchange chromatography and immobilized metal affinity chromatography with Zn²⁺. Crude FBPs were immunocoprecipitated with canine liver ferritin followed by the addition of anti-ferritin antibodies. Immunoglobulins in the immunocoprecipitate were detected with antibodies specific for human IgG, IgM or IgA heavy chains, and immunoglobulins IgG, IgM and IgA to bind to expressed recombinant human H and L chain homopolymers were also found. A portion of human serum proteins bound to zinc ions immobilized on beads were released upon the addition of canine liver ferritin, and the released protein was identified as IgM antibody. Additionally, the released proteins recognized peptide sequence (DPHLCDF) commonly found in amino acid sequences of mammalian ferritin H and L subunits. These results suggest that human serum contains anti-ferritin autoantibodies (IgG, IgM and IgA) which bind zinc ions and preferentially bind ferritin over both the H and L subunits, and that a portion of, but not all, the IgM antibodies bound to ferritin with higher affinity than to zinc ions and may recognize the common sequence found in mammalian ferritin H and L subunits. Full article

The production of human single-chain variable-fragments (scFvs) against carbohydrate antigens by phage display technology is seemingly a logical strategy towards the development of antibody therapeutics, since carbohydrates are self-antigens. Panning and screening of phages displaying human scFvs using a variety of neoglycolipids presenting structurally-defined carbohydrates resulted in a number of candidate phage clones as judged by cautious evaluation of DNA sequences and specific binding to carbohydrate moieties of interest. ScFv proteins were expressed in prokaryotic or eukaryotic cells from the respective genes. The characterization of isolated scFvs gene products after establishing expression, production and purification of scFv protein in different expression systems demonstrated that the production of scFv-human IgG₁ Fc conjugates were originally sufficient in the media of stably-transfected cells, but declined during early passages. Bacterial expression of soluble scFv proteins with binding activity suffered low yields, whereas overexpressed scFv proteins formed inclusion bodies, which required refolding. An insect cell expression system producing soluble and active scFv proteins was found to be cost- and time-effective. The best expression system and fine adjustments for the conditions to prepare active forms had to be determined for each scFv protein. The successful production of active scFv proteins seems to be dependent on their DNA and/or amino acid sequences. Full article

Alloimmunization is an undesirable iatrogenic effect of transfusion and transplantation. In fact, recipients can be considered as responders or not responders, in a continuum from tolerance, including organ transplantation and transfusion, to polyimmunized and refractory patients. New models and large studies have enabled a better understanding of the mechanisms that induce specific alloantibody (alloAb) generation. Here, we focus on risk factors of alloimmunization. We review the alloantibody characteristics, summarize the different leukocytes involved in their induction, and suggest some hypotheses. Full article

B lymphocyte receptors are generated randomly during the bone marrow developmental phase of B cells. Hence, the B cell repertoire consists of both self and foreign antigen specificities necessitating specific tolerance mechanisms to eliminate self-reactive B cells. This review summarizes the major mechanisms of B cell tolerance, which include clonal deletion, anergy and receptor editing. In the bone marrow presentation of antigen in membrane bound form is more effective than soluble form and the role of dendritic cells in this process is discussed. Toll like receptor derived signals affect activation of B cells by certain ligands such as nucleic acids and have been shown to play crucial roles in the development of autoimmunity in several animal models. In the periphery availability of BAFF, a B cell survival factor plays a critical role in the survival of self-reactive B cells. Antibodies against BAFF have been found to be effective therapeutic agents in lupus like autoimmune diseases. Recent developments are targeting anergy to control the growth of chronic lymphocytic leukemia cells. Full article

Targeted therapies for the treatment of cancer, but also inflammation and autoimmune diseases will reduce major side effects accompanied with conventional treatment modalities. The immunotoxin concept uses bacterial or plant toxins, coupled to antibodies or natural ligands targeting cancer cells. Initially, immunotoxins suffered from drawbacks like nonspecific cytotoxicity. Even the third generation of immunotoxins comprised of truncated antibodies and modified effector molecules experienced clinical set-backs due to immune responses. Long-term treatment of cancer and non-life-threatening chronic inflammatory diseases requires their complete ‘humanization’. This lead to evaluating human cytolytic fusion proteins (hCFPs), based on human apoptosis-inducing proteins. Lacking an endogenous translocation domain dramatically reduces the cell-death inducing capacity of such proteins. Here, we report on optimizing hCFPs, based on the anti-CD64 single chain variable fragment H22(scFv), specifically eliminating CD64+ macrophages and malignant progenitor cells. We replaced the bacterial toxin in H22(scFv)-ETA' with the pro-apoptotic human granzyme B or angiogenin. Translocation was promoted by a sophisticated adapter containing a membrane transfer peptide (MTD) flanked by endosomal and cytosolic cleavable peptides, thus achieving in vitro cytotoxic activity comparable to bacterial immunotoxins. We demonstrate for the first time that optimized hCFPs, based on granzyme B or angiogenin, can compete with classical ETA-based immunotoxins. Full article

The variety of chemically diverse pharmacologically-active compounds administered to patients is large and seemingly forever growing, and, with every new drug released and administered, there is always the potential of an allergic reaction. The most commonly occurring allergic responses to drugs are the type I, or immediate hypersensitivity reactions mediated by IgE antibodies. These reactions may affect a single organ, such as the nasopharynx (allergic rhinitis), eyes (conjunctivitis), mucosa of mouth/throat/tongue (angioedema), bronchopulmonary tissue (asthma), gastrointestinal tract (gastroenteritis) and skin (urticaria, eczema), or multiple organs (anaphylaxis), causing symptoms ranging from minor itching and inflammation to death. It seems that almost every drug is capable of causing an immediate reaction and it is unusual to find a drug that has not provoked an anaphylactic response in at least one patient. These facts alone indicate the extraordinary breadth of recognition of IgE antibodies for drugs ranging from relatively simple structures, for example, aspirin, to complex molecules, such as the macrolide antibiotics composed of a large macrocyclic ring with attached deoxy sugars. This wide recognition profile is borne out at the molecular level by results of quantitative immunochemical studies where hapten inhibition investigations have identified structural determinants complementary to IgE antibodies in the sera of allergic subjects. Allergenic determinants have been identified on a variety of drugs including neuromuscular blockers, penicillins, cephalosporins, opioids, thiopentone, sulfonamides, trimethoprim, quinolones, chlorhexidine and the non-steroidal anti-inflammatory drug aspirin. It is already clear that IgE can distinguish fine structural differences on a wide variety of molecules, determinants may be at least as small as an amino group or encompass the whole molecule, and individual drugs may demonstrate allergenic heterogeneity. Full article

ADP-ribosylation is an essential post-translational modification, mediated by a family of proteins named poly-ADP-ribose polymerases/Diphtheria toxin-like ADP-ribosyltransferases (PARPs/ARTDs), that functions to assist in cellular homeostasis through an array of mechanisms. Although the function of PARP1/ARTD1-mediated poly-ADP-ribosylation (PARylation) in response to environmental genotoxic stressors has been extensively studied, its role in the regulation and maintenance of cellular events under times of programmed DNA damage and repair remains to be elucidated. In the case of B cell maturation and differentiation, processes such as V(D)J recombination, somatic hypermutation, and class switch recombination, require the induction of DNA strand breaks for the generation of a varied immunoglobulin repertoire and, thus, serve as a model system to explore the function of PARylation in immunological processes. In this review, we summarize the current understanding of ADP-ribosylation and the PARPs/ARTDs family proteins, in particular PARP1/ARTD1-conferred PARylation, in B cells. Following an overview of PARylation in cellular responses to environmental and spontaneous DNA damage, we discuss the emerging function of PARP1/ARTD1 and PARylation in DNA damage-induced nuclear factor kappaB (NF-κB) signaling and B cell maturation and differentiation. Finally, we conclude by underlining further efforts that are needed to understand how the PARPs/ARTDs family proteins and ADP-ribosylation control the development and function of B cells. Full article

Invariant Natural killer T cell (iNKT cells) are a subset of T cells, which are narrowly defined as a T cell lineage expressing a semi-invariant CD1d-restricted T cell Receptors (TCRs) composed by Vα24-Jα18/Vβ11 in human, and Vα14-Jα18/Vβ8,Vβ7, and Vβ2 in mouse. Unlike conventional T cells which recognize peptides bound to highly polymorphic major histocompatibility complex (MHC) class I and II molecules, iNKT cells recognize lipid antigens, such as glycolipids, presented by CD1d, a non-polymorphic non-classical MHC class I molecule. Lipids derived from microbes, tumors, and allergens, as well as self lipids have been shown to be able to activate iNKT cells. Early on, in an immune response, ligation of the iNKT cell TCR leads to rapid and copious secretion of prototypical Th1 and Th2 cytokines. Moreover, like NK cells, iNKT cells express cytotoxic granules, such as perforin and granzyme that polarize upon activation of TCR and are able to kill target cells. Therefore iNKT cells are a very interesting subset of T cells that may bridge the innate and adaptive immune systems. Indeed, iNKT cells can mount specific responses to antigen with cytokine production and cytotoxic activity, however, their TCR evolved to recognize different glycolipid antigens in a conserved manner and to perform innate-like rather than adaptive functions. iNKT cells are now recognized as important players in atopic, autoimmune, infectious diseases, and cancer. Full article

Natural Killer (NK) cells, an important component of the innate immune system, can mount much more rapid responses upon activation than adaptive antigen specific responses. Among the various functions attributed to NK cells their effect on antibody production merits special attention. The modification of IgG subclasses distribution as well as the amplification of the B cell response can be functionally relevant both for mediation of antibody-dependent cellular cytotoxicity (ADCC) and for control of dysregulated autoantibody production. In this review recent experimental evidence for the mechanistic basis of the effect of NK cells on B cell-responses will be covered. Thus, it will be shown that these effects are mediated not only via activation of cytokine and Toll-like receptors (TLR), but also by direct receptor-ligand interactions. Importantly, the function of these receptor/ligands, CD48 and CD244, do not require recognition of class I-MHC molecules but are more dependent on inflammatory conditions brought about by infection or oncogenesis. Full article