B-Cells and T-Cells

What does a B-cell differentiate into when it is selected?

Plasma cells and memory cells

How many antibodies does a short-lived plasma cell produce?

2000 per minute

Describe the two types of plasma cells.

Short-lived (60%, do not live long), long-lived (40%, half life greater than 6 months, return to bone marrow)

Which type of plasma cell is shared with the fetus?

Long-lived

Which B-cells are more reserved for future infections?

Long-lived plasma cells and memory B-cells

What is the approximate half-life of memory B-cells?

5 years

What do antibodies specifically recognize?

Epitopes (sequence of 5-26 amino acids)

What characteristic apoprotein do B-cells have?

CD19

What is the approximate half-life of short-lived plasma cells?

A few days

Do antigens typically only have 1 epitope?

No, usually they have many

What is the base of the Y-shape of an antibody called?

Isotype region

What is the name for the region of antigen/epitope recognition?

Idiotype region

What does the isotype region determine?

Where the antibody will go in the body

How many isotype regions are there in humans?

G, M, E, D, A

List the general functions of antibodies

Opsonization, neutralization, aggregation, complement activation

What classification/destination is IgA?

Mucosal

What is the classification/destination of IgG?

Bloodstream

Describe the differentiation of short-lived plasma cells

One divides into multiple that produce each antibody isotype

Which antibody is produced following the first exposure to a pathogen?

IgM

Are IgM antibodies present in circulation?

Yes

Where are circulating antibodies present?

Blood and extracellular fluid

Where does IgM bind, and where is it more commonly found?

Surface of B-cells, higher on immature cells

Is IgG present in circulation?

Yes

Which type of plasma cell produces IgG during the first exposure to a pathogen?

Long-lived plasma cells

Which type of plasma cell produces IgM during the first exposure to a pathogen?

Short-lived plasma cells

Which antibody is produced more during the first exposure to a pathogen?

IgM

Which type of cell produces IgG during future exposures to the same pathogen?

Short-lived plasma cells (from memory B-cells)

Which type of cell produces IgM during future exposures to the same pathogen?

Short-lived plasma cells

Which antibody is produced more during future exposures to the same pathogen?

IgG

Which antibody can cross the placenta?

IgG

What percentage of antibodies in the blood are IgG?

75%

Are babies born with the mother’s plasma cells?

No, just antibodies

Describe the characteristics of IgA

Secretory, targets mucous membranes and breast milk

Describe the role of IgE

Binds to basophils/mast cells to increase specificity for future infections (involved in allergies)

How does IgE function with parasites?

Binds to them for eosinophil recognition

Which cells produce IgA?

Short-lived plasma cells

What influences how much IgG, IgM, and IgA are produced by short-lived plasma cells?

Site of infection

What percentage of an infant’s antibodies are IgA?

1% (what the mother is currently exposed to)

Which cells produce IgG during the first exposure to a pathogen?

Long-lived plasma cells

Which classes of IgG are produced for proteins?

IgG1, IgG3

Which classes of IgG are produced for polysaccharides?

IgG2

Which classes of IgG are produced for food allergens?

IgG4

Which antibody targets mucous membranes and breast milk (secretory)?

IgA

Which antibody binds to basophils and mast cells to increase future specificity?

IgE

Which antibody can bind to parasites?

IgE

Which antibody is most important for allergies?

IgE

What is a general function of IgD?

B-cell recognition and activation for the purpose of antigen presentation (“sample” of antibody the cell produces)

Which subtype of B-cell has a higher IgD content?

Mature naive B-cells

Explain the process of B-cell antigen presentation with regard to IgD

Antigen binds to IgD on cell surface, internalized and digested, placed on MHCII

Is IgD ever secreted?

No

Can B-cells do antigen presentation?

Yes

What is an example of a lipid antigen?

Lipopolysaccharide membrane

What is an example of a sugar antigen?

Polysaccharide capsule of bacteria

How do lipid/sugar antigens influence B-cells?

Directly activates the cell without any antigen presentation, induces differentiation into short-lived plasma cells

When lipid/sugar antigens stimulate B-cells, are memory cells produced?

No

How do lipid/sugar antigens influence B-cell receptors?

Bind directly to receptor, leading to cross-linking

Which antibody idiotype is activated when a non-protein antigen stimulates a B-cell?

IgM

Which cells notice bacteria first due to PAMPs?

Basophils and mast cells (then release histamine/leukotrienes/heparin)

Which cells notice bacteria first due to PAMPs?

Basophils and mast cells (then release histamine/leukotrienes/heparin)

What happens to long-lived plasma cells after the infection has been cleared?

Migrate back to bone marrow and keep producing IgG to manage potential reinfection

For a person with systemic lupus, what do their B-cells tend to recognize in error?

DNA

Which antibodies are produced during a food sensitivity/intolerance response?

IgG and IgA

Which antibodies are produced during a food allergy response?

IgE (immediate response)

What induces the class switching of antibody production by activated B-cells

What are monoclonal antibodies?

Produced in a cell culture of isolated B-cells

What is gamma globulin therapy?

The process of injecting a person with antibodies to a specific antigen

How long does gamma globulin therapy last?

3-6 months

What is the general purpose of injecting antibodies to Rh factor into the mother?

To prevent the creation of immune memory to Rh factor, which could lead to immunological attack during future pregnancies