Clonal Selection/Antibody Structure Flashcards
Specificity
The ability of adaptive immune cells (B and T lymphocytes) to only recognize specific portion of unique antigens. The innate immune system does not have the ability to specifically identify antigens.
Memory
The ability of the adaptive immune system to ‘remember’ specific antigens when they are encountered more than once. Memory B and T cells, which develop following antigen stimulation, are the basis of immune system’s more robust response to these antigens upon subsequent exposure.
Proliferation
Cellular proliferation refers to the expansion of a population of cells. In lymphocyte proliferation during clonal selection, only lymphocytes specifically activated by antigenic stimulation will multiply.
Effector Cells
Lymphocytes that are immediately capable of mounting a response to an antigenic challenge; as compared ton naive lymphocytes that must further proliferate and differentiate before they are capable of performing effector functions. Some examples of immune effector cells include: cytokine-secreting helper T cells, CTLs that are actively killing infected cells, and differentiated B cells that are secreting antibodies.
Memory Cells
Differentiated B or T lymphocytes that are initially formed after antigen stimulation of naive lymphocytes during a primary immune response. In subsequent exposures to the same antigens, memory cells are able to survive in a functionally quiescent state for many years between antigen exposures.
Immunoglobulin (Ig)
Also known as an antibody (Ab), an immunoglobulin is a membrane bound or soluble protein produced by B cells or plasma cells respectively. When membrane bound, an immunoglobulin acts as a B cell receptor (BCR). Soluble immunoglobulins act to opsonize antigens, participate in antibody-dependent-cell-mediated cytotoxicity (ADCC), neutralize virus and toxins, and activate complement. A particular antibody is specific for one epitope on an antigen.
Plasma
Uncoagulated blood from which the cells have been removed.
Serum
Fluid remaining from blood after removal of cells, fibronogen, and clotting factors by clotting
Bivalency
This term describes the characteristic feature that each individual antibody possesses two identical antigen-binding sites.
Antigen-binding site
the region of an antibody, B or T cell receptor that directly interacts with an antigen. Also call “antibody combining site”.
Variable region
The extracellular, N-terminal region of an Ig heavy or light chain or a TCR alpha, beta, or delta chain that contains variable amino acid sequences that differ among every clone of lymphocyte and that are responsible for the specificity of antigens.
Constant (C) region
the carboxyl-terminal portion of Ig (heavy or light chain) or TCR polypeptide chain that is not involved in antigen binding and odes not vary in sequence among different clones.
Idiotype
A classification of immunoglobulins that share the same specific antigenic binding site, as is determined by the variable portion of the receptor.
Isotype
An Ig isotype (also known as Ig class) is a classification of immunoglobulins that share the same heavy chain constant region. In mammals there are five basic isotypes (IgM, IgD, IgG, IgA, and IgE), however different species have their own subclasses. Different isotypes have varying structural and functional characteristics. The isotype profile detected in a patient’s serum can indicate a particular type of immune response.
J chain
The J chain (aka the joining chain) is a polypeptide that holds polymeric Ig together (pentameric IgM molecules or dimeric IgA molecules). Only one J chain is needed for each polymeric Ig molecule.
Neoplastic
this term describes cells that are characteristic of tumor or cancerous cells
Adaptive immune response
the response of antigen-specific lymphocytes to antigen, including the development of immunological memory. Adaptive immune responses are generated by clonal expansion of lymphocytes. Adaptive immune responses are distinct from innate and non-adaptive phases of immunity, which are not mediated by clonal selection of antigen-specific lymphocytes. Adaptive immune responses are also known as acquired immune responses.
Antibody (Ab)
Plasma protein that bind specifically to particular molecules known as antigens. Antibody molecules are produced in response to immunization with an antigen. They are the specific molecules of the humoral immune response that bind to and neutralize pathogens or prepare them for uptake and destruction by phagocytes. Each antibody molecule has a unique structure that allows it to bind to its specific antigen, but all antibodies have the same overall structure and are known collectively as immunoglobulins.
Antigen (Ag)
Molecules that react with antibodies. Their name arises from their ability to generate antibodies. However, some antigens do not, by themselves, elicit antibody production; only those antigens that can induce antibody production are called immunogens.
Antiserum (Plural = Antisera)
Serum contains polyclonal antibodies against many different antigens. If we have immunized an animal with a particular antigen, and the animal has generated polyclonal antibody response to that antigen, then the animal serum is an antiserum against the antigen. Therefore, antiserum us serum containing antibodies against specific antigens. For example, antiserum against tetanus toxin has antibodies against the tetanus toxin.
Polyclonal and monoclonal antibodies
Polyclonal antibody (response) against an antigen represents a collection of antibodies from different B cells that recognize multiple epitopes on the same antigen. Antibody response generated following immunization or infection is a polyclonal antibody response. In contrast, a monoclonal antibody represents antibody from a single antibody producing B cell, and therefore, it only binds with one unique epitope.
Class (isotype)
Human immunoglobulins are divided into five principal classes based on chemical properties conferred by distinct heavy chain constant regions. The five subclasses are IgM, IgG, IgA, IgE, and IgD. The IgG subclass includes four subclasses and IgA includes two subclasses. Immunoglobulin classes are also called isotypes.
B cells (B lymphocytes)
One of the two major classes of lymphocytes. The antigen receptor on B lymphocytes, B cell receptor (BCR), is a cell-surface immunoglobulin molecule. Upon activation by antigen, B cells differentiate into cells producing antibodies of the same specificity as their initial B cell receptor.
Clone
A population of cells all derived from a common progenitor.
Clonal expansion
Clonal expansion is the proliferation of antigen-specific lymphocytes in response to antigenic stimulation and precedes their differentiation into effector cells. It is an essential step in adaptive immunity, allowing rare antigen-specific cells to increase in number for that they can effectively combat that pathogen that elicited the response.
Clonal Selection Theory
The central paradigm of adaptive immunity. It states that adaptive immune responses derive from individual antigen-specific lymphocytes that are self-tolerant. These specific lymphocytes proliferate in response to antigen and differentiate into antigen-specific effector cells to eliminate the eliciting pathogen, and memory cells to sustain immunity.
Complementarity Determining Region
The part of V region of an antibody molecule that makes contact with a specific ligand and determines its specificity. The CDRs are the most variable part of the receptor protein, giving receptors their diversity, and are carried on six loops at the distal end of the receptor’s variable domains, three loops coming from each of the two variable domains of the receptor.
Epitope (antigenic determinate)
the precise site on an antigen that interacts with an antibody’s antigen-binding site is referred to as an epitope.
Hinge region
a region of the immunoglobulin heavy chain which joins the Fab arms to the Fc piece. The hinge permits flexibility of the Fab arms.
Ig Domains (Ig-fold)
The characteristic feature of proteins of the immunoglobulin superfamily or proteins that include antibodies, T-cell receptors, MHC molecules, and many other molecules. The immunoglobulin domain comprises two beta-pleated sheets held together by a disulfide bond.
Immunological Memory
The speedier and more effective immune response when antigen is encountered more than once. This memory is both specific and long-lived.
Innate immunity
Mechanisms that mediate resistance to infection, do not discriminate between pathogens, and do not increase with repeated exposure to a pathogen.
Macrophages
Large mononuclear phagocytic cells important in innate immunity, in early non-adaptive phases of host defense, as antigen-presenting cells, and as effector cells in humoral and cell-mediated immunity. They are derived from monocytes and are found in most tissues of the body. They play a critical role in host defense.
Mature B Cells
B cells that have acquired surface IgM and IgD and have become able to respond to antigen. Also called naive B cells
Monocytes
White blood cells with a bean shaped nucleus which are precursors to macrophages
Monoclonal Antibody
Antibodies produced by a single clone of B lymphocytes. Monoclonal antibodies are usually produced by making hybrid antibody-forming cells from fusion of myeloma cells with immune spleen cells.
Multiple Myeloma
A tumor of plasma cells, almost always first detected as multiple foci in bone marrow. Myeloma cells produce a monoclonal immunoglobulin called a myeloma protein which is detectable in the patient’s plasma.
Myeloma Protein
The secreted immunoglobulin products of myeloma tumors that are found in the patient’s plasma.
Naive Lymphpcyte
Lymphocytes that have never encountered their specific antigen and thus have never responses to it, as distinct from memory or effector lymphocytes. All lymphocytes leaving the primary lymphoid organs are naive lymphocytes, those from the thymus being naive T cells and those from the bone marrow being naive B cells.
Peyer’s Patched (secondary lymphoid organ)
Aggregates of lymphocytes along the small intestine, especially in jejunum in ruminants, pigs, dogs, and horses. Peyer’s patches in the terminal ileum have a primary lymphoid organ function.
Plasma cell
Plasma cells are terminally differentiated B lymphocytes. Plasma cells are the main antibody-secreting cells of the body. They are found in the medulla of the lymph nodes, in splenic red pulp, and in bone marrow. Malignant plasma cells form multiple tumors in bone marrow and are called multiple myeloma.
Secretory Component
A polypeptide chain that is part of a secretory IgA molecule (SIgA). SIgA is an IgA dimer found in secretions and mucosal surfaces.
T cells (T lymphocytes)
A subset of lymphocytes defines by their development in the thymus and by heterodimeric receptors associated with the proteins of the CD3 complex.
Variable region (V region)
The most distal amino-terminal domain of an antibody heavy or light chain. The V region of the light chain is encoded by gene segments V and J, and that heavy chain by the gene segments V, D, and J during B cell development.
