Humoral Immunity and Microbial Recognition

Flashcards for Humoral Immunity and Microbial Recognition lecture review.

What do afferent lymphatic vessels transport?

Lymph fluid containing antigen-carrying dendritic cells, particulate antigen and a few lymphocytes are transported from tissues to regional lymph nodes.

Where do efferent lymphatic vessels transports lymph fluid?

Lymph fluid from lymph nodes travels into venous circulation via the thoracic duct.

What is the function of efferent lymphatic vessels?

Secrete antibodies, activated/memory T cells and B cells throughout the body fight off infection.

What is the function of lymph nodes?

Site of generation of T cell response and B cell antibody response to specific antigen, interact with antigens and antigen-presenting cells

What is the function of phagocytosis in the lymph node?

Particulate matter that enters prevents their entry into blood stream

What is the function and structure of the spleen?

Immune responses are mounted against antigens in the blood, and old/defective RBCs are phagocytosed and recycled.

Where is the location of the spleen?

Upper left quadrant of the abdominal cavity.

What does the spleen consist of?

White pulp and red pulp separated by a marginal zone.

What is the function of the white pulp of the spleen?

Generation of T cell responses and B cell responses (antibodies) against blood-borne antigens.

What is the role of interdigitating dendritic cells in the marginal zone of the spleen?

Trap blood-borne antigens and transport them to the white pulp.

What occurs in the red pulp of the spleen?

Defective/old RBCs and blood-borne pathogens are phagocytosed by macrophages.

What is Humoral immunity?

Mediated by macromolecules found in extracellular fluids such as secreted antibodies, complement proteins, and certain antimicrobial peptides.

What are cytokines and chemokines?

Proteins that communicate among cells of the immune system.

What are Chemokines?

Cytokines that attract cells with the appropriate receptors to regions where the chemokine concentration is the highest.

What can cytokines cause?

Changes in the expression of adhesion molecules and chemokine receptors on the target membrane, induce the cell to proliferate of differentiate, survive or die or to modulate its effector functions

What determines the sensitivity of a target cell to a particular cytokine?

The presence of specific cytokine receptors

What are the functions of Cytokines?

Small proteins that mediate the effector functions of the immune system.

What is Endocrine action?

Released into the bloodstream to affect distant cells.

What is Paracrine action?

Released to affect nearby cells.

What is autocrine action?

Released, but then bind to receptors on the cell that produced them.

What are Redundant cytokines?

Multiple cytokines exerting similar actions/same message on the same target set.

What are Synergistic cytokines?

Two (or more) that work together to induce an effect.

What are Antagonistic cytokines?

Can inactivate the effect of another.

What are Chemokines?

Small proteins that direct leukocyte migration.

What are Chemokine receptors an example of?

G protein coupled receptors (GPCRs).

What is the function of Chemokines?

Generate the movement of immune cells. Immune cells are attracted higher concentrations of chemokines.

What therapies are used to treat Rheumatoid Arthritis?

Soluble TNF-alpha receptor (Enbrel). Monoclonal antibodies against the receptor (Remicade and Humira)

Which therapies are used to treat Multiple Sclerosis?

IFN-Beta has emerged as the first drug capable of producing clinical improvement in MS.

Which therapies are used for the Prevention of Transplant Rejection?

Monoclonal antibodies against the alpha chain of IL-2R (Simulect and Zenapax)

What are Antigens?

Substances that react with antibodies of TCRs.

What are immunogens?

Substances that induce an immune response.

What are Haptens?

Small molecules, are not immunogens

Which type of molecules are good immunogens?

Complex proteins and carbohydrates

Which molecules are usually excellent immunogens?

Insoluble molecules or aggregates

What is the effect of dose of an immunogen during the recognition of antigens?

A large oral does of an immunogen may induce tolerance rather than immunity.

What is an antigenic determinant or epitope?

A distinct portion of the molecule

What type of protein sequences are recognized by TCRs?

Only short peptide sequences

What is Affinity?

Measures the strength of interaction between an epitope and an antibody’s antigen binding site

What is Avidity?

Measure of the overall strength of an antibody- antigen complex.

What is the measure of Avidity?

Dependent on three major parameters: The affinity of the antibody for the epitope, valency of both the antibody and antigen and the structural arrangement of the parts that interact.

What is the characteristics of B cells?

Bear membrane-bound receptors that share the same antigen-binding site as the secreted antibody.

What shape are Antibodies and what peptides form this shape?

Heavy chain and the light chain

What region is at the top of the chains, which are the antigen-binding sites?

The variable region

What are the ends of the Y in the structure of the heavy chain?

The Fab fragment and the Fc fragment

What are the functions of the Fab and Fc of a heavy chain?

The Fab determines recognition and Fc determines function.

What are Isotype classes?

IgG, IgD, IgE, IgA (dimer), and IgM (pentameter)

Which is the first antibody that a B cell produces when it encounters an antigen?

IgM

What is the role of antibodies?

Neutralize pathogens and toxins preventing them from binding to cells.

What is Opsonization for phagocytosis?

When a bacteria is surrounded by an antibody it is called a sugar/candy coat which allows macrophages to see that bacteria better and then do phagocytosis to eliminate the pathogen faster

How does an antibody bind to the pathogen during Fixation of the Complement?

Interact with the complement making the complement more stable and allows lysis to occur faster

How do antibodies block attachment of Viruses to cause infection?

Acts as an obstacle between the interaction of the virus and receptor which prevents attachment and the invasion of the virus in the cell

How do antibodies neutralize toxins?

They can surround the molecule and let the toxin precipitate so that the toxin can’t enter the cell

What are the features of IgG antibodies?

Monomer makes up 70-75% of the total Ig pool, fixes the complement well, blocks attachment well and is greatat opsonization and passes through placenta

What are the features of IgM antibodies?

Pentamer makes up 10% of total Ig pool and is excellent at fixing complement and blocking attachment and appears in early infection and wanes quickly.

What are the characteristics of IgA antibodies?

Dimer makes up 15% of total Ig pool, protects mucous membranes in lung and gut and is great at blocking attachment.

What are the characteristics of IgE antibodies?

Produced during allergic reactions and is not good at the four functions

Which event do B and T cells have that is rare in the somatic cell, which occurs in the germline?

Somatic recombination

What is the role when the immune cell is activated?

When an immune cell is activated, the genomic region where these genes are sitting start to be chopped. the cell chooses the constant chain, joint, diversity and variable

What is Somatic hypermutation?

To increase the diversity of antibody genes in B cells to produce high-affinity antibodies.

What does the CDR3 region determine?

Intensity of the interaction between recognizing the epitope and the groove of the antibody/BCR

What is the complement system?

A set of circulating, inactive proteins that are sequentially activated in response to a pathogen and bind to the surface of the microbe resulting in death.

What are the three pathways of complement activation?

Classical, Mannose-binding lectin mediated, and Alternative

When is the classical pathway intiated?

Initiated when complement binds to antibodies that are attached to a pathogen

How does the Lectin pathway begin?

MBL protein that recognizes lectin which recalls the C2C4 to form C3 convertase

How does the Alternative Pathway begin?

Begins with spontaneous hydrolysis of C3 breaking it into C3b and C3a