Immunology: Antibodies

What are antibodies? What do they bind?

• the secreted form of a B cell’s antigen receptor

• they most commonly bind to carbohydrates and proteins

• can disable pathogen and make it susceptible to destruction by other parts of the immune system

Why are antibodies important for defense against extracellular pathogens

• during an adaptive immune response, antibodies are responsible for clearing extracellular pathogens and their toxins

What is opsonization

• the tagging of pathogens caused by antibodies coating pathogen and “tagging” them for destruction

What is agglutination?

the process where antibodies cause the clumping of particles like red blood cells or vacteria

What are immunoglobulins?

• antibodies

What type of cell makes immunoglobulins

• plasma cells

what is agammaglobulinemia

• the inability to produce immunoglobulins

• patients with this condition are highly susceptible to various infections

what to antibodies look like

• made up of four polypeptide chains; two heavy chains and two light chains

• each of these chains has a variable and constant region

• variable region is where the antigen binds

• constant regions interact with other components of the immune system

what are antibody isotypes

• a class of antibody, like IgG IgA IgE IgM or IgD, determined by the heavy chain region

what are the five different antibody isotypes

• IgG

• IgM

• IgA

• IgD

• IgE

characteristics of IgG

• most abundant antibody in internal body fluids

• highest opsonization and neutralization activity

characteristics of IgM

• initial B cell receptor

• secreted from is a pentamer and binds with overall strong avidity even if the individual affinity is low

characteristics of IgA

• found on mucosal surfaces, in the lumen of the gut, and in tears, saliva, sweat, and breast milk

• forms a dimer after secretion and is made more than any other isotype

characteristics of IgD

• concentrated in the upper airways/bronchial tract

• the Fc region binds to basophils, triggering them to elicit an effector function when antigen binds

Characteristics of IgE

• the Fc portion binds to mast cells in the epithelium, eosinophils at mucosal surfaces, and basophils in the blood

• upon antigen binding, it elicits a strong inflammatory response and is critical for fighting parasitic infections

what is the hinge region and why is it important

the flexible part of the antibody that allows it to bind with both arms to many different arrangements of antigen

what are Fab and Fc fragments

• Fab fragments are responsible for binding to the antigen

• Fc fragment mediates effector functions

what is the 12/23 rule and why is it important

• recombination only occurs between two RSS that have different spacer lengths of either 12 or 23 base pairs

what are palindromic nucleotides

• nucleotide sequences that read the same forward as they do backward

what are non-templated nucleotides

• nucleotides added to a nucleic acid without a corresponding sequence on the original DNA template

what is a primary lymphoid follicle

• a dense aggregation of resting, naive B cells, supporting T cells, and follicular dendritic cells in the cortex of a lymph node

what is a secondary lymphoid follicle

• an active B cell concentration in the body’s immune organs that has a developed germinal center in response to antigen stimulation

what is isotype switching and how does it work

• the process of switching the type of antibody produced without changing antigen specificity

• immature B cells leave the bond marrow expressing the IgM isotype

• when a B cell encounters an antigen in a secondary lymphoid organ, it undergoes isotype switching

• isotype switching occurs in the secondary lymphoid follicle

what is somatic recombination

• somatic recombination is the process by which various B cell receptor and antibody gene segments are combined into a functional gene

What is affinity maturation

• when B cells undergo rounds of mutation and selection to produce antibodies with higher binding affinity to a specific antigen

What are the different ways that antibody diversity is achieved

• random recombination of heavy and light chain variable and constant regions