What is an antibody?

What is the function of an antibody?

To bind to a pathogen or a product produced by a pathogen

1. What is an antigen with only one epitope? 2. What is an antigen with multiple copies of the same epitope? 3. What is an antigen with different epitopes

1. Monovalent antigen 2. Multivalent antigen 3. Multivalent antigen

What are some of the types of differences in the type of antibody structure?

1. Number of heavy chain immunoglobulin domains 2. Location of disulfide bonds linking the chains 3. Presence of a hinge region in the heavy chain 4. Number and location of N-linked carbohydrate groups 5. Number of molecules present in secreted form

1. What can cleave a hinge region in an antibody? 2. What happens when it is cleaved?

1. Proteolytic cleavage by the enzyme PAPAIN occurs on the N-terminal side of the disulfide bonds that link the immunoglobulin heavy chains. a. the arms are then called Fab or fragment antigen binding, which still has affinity to bind to the antigen b. the stem is now called the fragment crystallizable (Fc) region, which has no affinity for antigen 2. Proteolytic cleavage by the enzyme DEPSIN occurs on the C-terminal side of the disulfide bonds that link the immunoglobulin heavy chains a. the arms are now called F(ab')2 - they have the same binding avidity to antigens as original antibody b the stem is now Fc, and still no affinity for antigen

1. what do the lymphocytes recognize? 2. What is the definition

1. They recognize antigens 2. Any molecule or part of a molecule from bacteria, viruses or other disease-causing pathogens that is specifically recognized by highly specialized lymphocyte recognition proteins - they usually recognize proteins and carbohydrates

1. What is the part of an antigen that binds to an antibody called? 2. What are the different ways an antigen interacts with an antibody?

1. antigenic determinant or epitope: the part of an antigen to which an antibody binds - this area is composed of a small stretch of amino acids or a small region of a polysaccharide chain 2. a. Pocket: antibody binds a small compact epitope, such as a terminal sugar ( sphere type) b. Groove: antibody that binds to several adjacent sugars uses a long shallow groove (cylinder like) c. Extended surface: antibody that binds to an extended surface, surface to surface, not an end point like the top two. d. Protruding surface: the epitope is a pocket in the antigen, the antibody is almost pick like

1. What lineage builds the adaptive effectors cells? a. Lymphoid b. Myeloid c. Erythroid

1. the lymphoid

What is the difference between affinity and avidity?

Affinity is the strength of binding at a single site Avidity is the overall strength of binding with multiple binding sites

What is and when does adaptive immunity begin

- response initiates late, 96 hours after infection, but it is highly specific to the pathogen - it takes a long time because the body has to make it specifically for the pathogen

What are the type types of epitopes for protein antigens?

1. Linear epitopes: are composed of several successive amino acids in a protein sequence 2. Discontinuous or conformational epitopes: two or more parts of the protein antigen that are separated in the amino acid sequence but are brought together in the folded protein - most likely to occur

1. What is the structure of an antibody? 2. What is the structure composed of? - how can it be divided? - types of classes 3. What is the unique protein sheet created?

1. A Y-shaped glycoprotein composed of 4 polypeptide chains - the top portion is referred to as the arms, and the top is called the N termini - the bottom portion is referred as the stem, and the end is called the C termini - 2 disulfide bonds hold the heavy chains together 2. 2 identical heavy chains (H) and 2 identical light chains (L) - each segment/domain consists of 110 amino acids and is termed an immunoglobulin domain (Ig domain) a. every light chain can be divided by domain type. Each contains a Variable light (Vl) and a Constant light (Cl) - the 2 isotopes or classes are either Lambda or Kappa - An antibody will contain 2 lambda or 2 kappa light chains, but NEVER a mix of the two - ALL light chains consist of 2 immunoglobulin domains b Every heavy chains contains 1 Variable heavy (Hv) and 3 constant heavy numbered numerically away from the variable region (Ch1, CH2, CH3) - there are 5 isotypes of classes: gamma (immunoglobulin G; IgG); Mu (immunoglobulin M; IgM); Alpha(immunoglobulin A; IgA); Delta (immunoglobulin D; IgD); Epsilon (immunoglobulin E; IgE) 3. Each domain contains a structure where two B-sheets are folded onto each other and covalently linked by a disulfide bond, like a b sandwhich

What is the task of the arms in the antibody and the stems?

1. Arms of the immunoglobulin interacts with specific antigens and vary in sequence; therefore, they are termed the variable (v) region. - the top part of the arms interacts with the antigen, by increasing the number of binding sites, we increase Avidity - an arm has 2 binding sites/molecule ( a Vh and Vl)2. The stem of the immunoglobulin interacts with effector molecules and cells and are more constant in sequence; therefore, they are termed the Constant region (C)

1. What are the effector cells that make up the adaptive immunity?

1. B cells, which originate in the bone marrow 2. T-cells which originate in the thymus 3. NK cells are also part of the lymphoid lineage but are part of the innate immunity

1. What type of interactions are at play for the antigen to antibody binding? 2. How can these be removed?

1. Binding of antigen to antibody occurs through noncovalent interactions and is therefore reversible a. electrostatic forces b. hydrogen bonds c. van der waals forces d. hydrophobic forces 2. High salt concentrations, pH extremes, detergents and even competition with high concentrations of pure antigen/epitopes can cause dissociation

How variable are the light and heavy chain variable regions

1. Each variable region can be divided into a hypervariable region (HV) or a framework region (FR) a. the hypervariable region are found in each domain, and are located at the three loops that are exposed at the end of the domain farthest from the constant region - each VR has 3 HV - this is what interacts with the antigen - they are also called CDRs or complementary-determining regions - the differences in the loops between different antibodies create both the specificity of antigen-binding sites and their diversity b the framework region is much less variable, but each VR has 4 FR

1. What type of immunity does a B cell provide? - they different types of molecules that aid in immunity - what is it good for 2. What type of immunity does a T-cell provide? - what is it good for

1. Humoral immunity - they make antibodies or immunoglobulins (Igs) - they can be membrane bound B-cell receptor (BCR) or secreted antibodies which are identical in structure to BCR - they are good for dealing with extracellular pathogens and secreted toxic products 2. Cell-mediated immunity - it for direct interactions with cells - they have TCR or T-cell receptors - good for dealing with intracellular pathogens

How is the affinity of antigen to antibody determined

The affinity of a single antigen-binding site of an antibody for an epitope is determined by the sum of the non-covalent forces (attractive and repulsive) between the two molecules

What is the hinge region on an antibody for?

The hinge region of antibodies like IgG provides the immunoglobulin with flexibility for binding to its specific antigen - the more antibodies that can bind to an antigen the stronger the binding - it also allows it to bind wit both arms to many different arrangements of antigens on the surfaces of pathogens

What is the antibody repertoire?

The total number of different specific antibodies that can be made by an individual. - in humans at least 10^11