Clonal Selection/Antibody Structure

Question 1

Specificity

Answer 1

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.

Question 2

Memory

Answer 2

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.

Question 3

Proliferation

Answer 3

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.

Question 4

Effector Cells

Answer 4

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.

Question 5

Memory Cells

Answer 5

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.

Question 6

Immunoglobulin (Ig)

Answer 6

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.

Question 7

Plasma

Answer 7

Uncoagulated blood from which the cells have been removed.

Question 8

Serum

Answer 8

Fluid remaining from blood after removal of cells, fibronogen, and clotting factors by clotting

Question 9

Bivalency

Answer 9

This term describes the characteristic feature that each individual antibody possesses two identical antigen-binding sites.

Question 10

Antigen-binding site

Answer 10

the region of an antibody, B or T cell receptor that directly interacts with an antigen. Also call “antibody combining site”.

Question 11

Variable region

Answer 11

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.

Question 12

Constant (C) region

Answer 12

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.

Question 13

Idiotype

Answer 13

A classification of immunoglobulins that share the same specific antigenic binding site, as is determined by the variable portion of the receptor.

Question 14

Isotype

Answer 14

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.

Question 15

J chain

Answer 15

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.

Question 16

Neoplastic

Answer 16

this term describes cells that are characteristic of tumor or cancerous cells

Question 17

Adaptive immune response

Answer 17

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.

Question 18

Antibody (Ab)

Answer 18

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.

Question 19

Antigen (Ag)

Answer 19

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.

Question 20

Antiserum (Plural = Antisera)

Answer 20

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.

Question 21

Polyclonal and monoclonal antibodies

Answer 21

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.

Question 22

Class (isotype)

Answer 22

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.

Question 23

B cells (B lymphocytes)

Answer 23

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.

Question 24

Clone

Answer 24

A population of cells all derived from a common progenitor.

Question 25

Clonal expansion

Answer 25

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.

Question 26

Clonal Selection Theory

Answer 26

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.

Question 27

Complementarity Determining Region

Answer 27

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.

Question 28

Epitope (antigenic determinate)

Answer 28

the precise site on an antigen that interacts with an antibody's antigen-binding site is referred to as an epitope.

Question 29

Hinge region

Answer 29

a region of the immunoglobulin heavy chain which joins the Fab arms to the Fc piece. The hinge permits flexibility of the Fab arms.

Question 30

Ig Domains (Ig-fold)

Answer 30

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.

Question 31

Immunological Memory

Answer 31

The speedier and more effective immune response when antigen is encountered more than once. This memory is both specific and long-lived.

Question 32

Innate immunity

Answer 32

Mechanisms that mediate resistance to infection, do not discriminate between pathogens, and do not increase with repeated exposure to a pathogen.

Question 33

Macrophages

Answer 33

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.

Question 34

Mature B Cells

Answer 34

B cells that have acquired surface IgM and IgD and have become able to respond to antigen. Also called naive B cells

Question 35

Monocytes

Answer 35

White blood cells with a bean shaped nucleus which are precursors to macrophages

Question 36

Monoclonal Antibody

Answer 36

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.

Question 37

Multiple Myeloma

Answer 37

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.

Question 38

Myeloma Protein

Answer 38

The secreted immunoglobulin products of myeloma tumors that are found in the patient's plasma.

Question 39

Naive Lymphpcyte

Answer 39

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.

Question 40

Peyer's Patched (secondary lymphoid organ)

Answer 40

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.

Question 41

Plasma cell

Answer 41

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.

Question 42

Secretory Component

Answer 42

A polypeptide chain that is part of a secretory IgA molecule (SIgA). SIgA is an IgA dimer found in secretions and mucosal surfaces.

Question 43

T cells (T lymphocytes)

Answer 43

A subset of lymphocytes defines by their development in the thymus and by heterodimeric receptors associated with the proteins of the CD3 complex.

Question 44

Variable region (V region)

Answer 44

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.