Characterization of Glycoproteins with the Immunoglobulin Fold by X-Ray Crystallography and Biophysical Techniques
1Institute of Applied Biosciences, Centre for Research and Technology Hellas, 2Department of Immunology, Genetics and Pathology, Science for Life Laboratory, Uppsala University, 3Department of Molecular Medicine and Surgery, Karolinska Institutet, 4Division of Immunology, Transplantation and Infectious, IRCCS San Raffaele Scientific Institute, 5Department of Immunology, Laboratory for Medical Immunology, Erasmus University Medical Center, 6Hematology Department, Nikea General Hospital, 7Assistance publique - Hôpitaux de Paris (AP-HP), Hopital Pitié-Salpêtrière, Department of Hematology, and UPMC University Paris 06, UMRS 1138, 8Division of Experimental Oncology, IRCCS Istituto Scientifico San Raffaele and Università Vita-Salute San Raffaele
1Department of Medicine, Weill Cornell Medical College, 2Institute for Computational Biomedicine, Weill Cornell Medical College, 3Department of Pathology and Laboratory Medicine, Weill Cornell Medical College
We speak of an allergy when the immune system triggers a response against a benign foreign structure, like food, pollen or pet dander. These elicitors are called allergens. If the immune system of a hypersensitive individual was primed against a specific allergen, it will trigger allergic symptoms during every subsequent encounter of the allergen. Symptoms can be mild, such as hay fever, to severe, such as potentially fatal anaphylactic shock. The immune system is crucial for defending an organism against bacteria, viruses, fungi, toxins, and parasites. However, in a hypersensitive response, it can be triggered by harmless substances and cause unpleasant or potentially life-threatening overreactions, called allergies. The first step toward establishing an allergy is sensitization. For instance, an individual becomes allergic to the pollen of ragweed when, for the first time, immune cells in the respiratory passage take up the pollen and degrade the allergens into fragments. These immune cells are called antigen-presenting cells, or APCs, because they display the degraded allergen fragments on their surface. Examples of APCs are dendritic cells, macrophages and B cells. Subsequently, APCs activate encountered Type 2 helper T cells (Th2). The activated Th2 then release chemical signals (e.g., cytokines) that cause B cells to differen…
Antibodies, also known as immunoglobulins (Ig), are essential players of the adaptive immune system. These antigen-binding proteins are produced by B cells and make up 20 percent of the total blood plasma by weight. In mammals, antibodies fall into five different classes, which each elicits a different biological response upon antigen binding.
Antibodies consist of four polypeptide chains: two identical heavy chains of approximately 440 amino acids each, and two identical light chains composed of roughly 220 amino acids each. These chains are arranged in a Y-shaped structure that is held together by a combination of covalent disulfide bonds and noncovalent bonds. Furthermore, most antibodies carry sugar residues. The process of adding sugar side chains to a protein is called glycosylation. Both the light chain and heavy chain contribute to the antigen binding site at each of the tips of the Y structure. These 110-130 amino acids are highly variable to allow recognition of an almost unlimited number of antigens. This region is also called the variable region and is part of the antigen binding fragment. Each arm of the Y-shaped unit carries an identical antigen binding site. Antibodies can crosslink antigens: when one arm binds to one antigen and the other arm binds to a second, structurally identical antigen. Crosslinking is facilitated by the f…
1PARCC-INSERM U970, Université Paris Descartes, 2INSERM U970, Université Paris Descartes, 3Equipe Labellisée Ligue Contre le Cancer, 4Department of Immunology, Hopital Européen Georges Pompidou, 5Department of Medical Urology, Hopital Européen Georges Pompidou, 6Department of Pathology, Hopital Européen Georges Pompidou, 7Université Paris Diderot Paris 7, 8Department of medical oncology, Hopital Européen Georges Pompidou