B cell maturation

1. proliferation of immature cells

2. expression of antigen receptor genes

3. selection of lymphocytes that express useful antigen receptors

what events are common to B and T lymphocyte maturation?

hematopoietic stem cells

what is the origin of B cells?

bone marrow

where do B cells mature?

antigen-independent lymphopoiesis

what is the process of B cell maturation called?

10-15%

what percent of peripheral blood lymphocytes are B cells?

changes in expression of cell markers

what helps distinguish each phase of B cell maturation?

B cell programmed to produce a unique antibody molecule

what is the end result of B cell maturation?

signaling to regulate B cell development and activation

what is the function of CD19?

thought to be involved in B cell activation

what is the function of CD20?

receptor for complement breakdown component

what is the function of CD21?

found on activated T and B cells; receptor for IL-2; it is a growth factor made by T cells

what is the function of CD25?

interact with Th cells; present on all stages except on plasma cell

what is the function of MHC II?

found on most nucleated cells

what is the function of MHC I?

found on all hematopoietic cells; involved in activation

what is the function of CD 45R?

2 heavy and 2 light chains

what is the basic unit of a B cell antibody?

• G (γ); M (µ)

• A (⍺); D (δ)

• E (ε)

what are the heavy chains of a B cell antibody?

• kappa (κ)

• lambda (λ)

what are the light chains of a B cell antibody?

• constant

• variable

what are the regions of a B cell antibody?

1. lymphoid stem cell

2. pro-B cell

3. pre-B cell

4. immature B cell

5. mature B cell

what are the sequential steps of B cell maturation?

pro-B cell

what is the first recognizable cell in B-cell line?

formation of µ (mu); IgM heavy chain

what is the pro-B cell committed to?

bone marrow stromal cells

what produces cytokines?

formation of µ heavy chains

what signals the beginning of the pre-B cell?

formation of light chains

what do pre-B cells commit to?

to stimulate proliferation and further maturation

why do µ heavy chains and surrogate light chains form pre-B cell receptors?

immature B cell

what cell has a complete IgM molecule on its surface?

variable regions on heavy and light chains

what determines specificity in immature B cells?

no longer in cytoplasm

where is µ in immature B cells?

formation of IgD

what are immature B cells committed to?

self-reacting—cells that bind to self antigens

what kind of B cells are eliminated during recombination?

apoptosis

how are self-reacting B cells eliminated?

IgD + IgM

what does a mature B cell receptor express?

cross linking

what needs to happen for mature B cells to become activated?

secondary lymphoid organs

where do mature B cells go?

cell dies within a few days

what happens when a mature B cell cannot contact its specific antigen?

cell becomes activated

what happens if a mature B cell interacts with the appropriate antigen?

antigen dependent lymphopoiesis

what do activated B cells undergo after traveling to secondary lymphoid organs?

B cell receptor

what produces the first activation signal for activated B cells?

• thymus independent antigens

• thymus dependent antigens

what produces the second activation signal for activated B cells?

plasma cells or memory cells

what do activated B cells differentiate into?

protein antigen

what is the most complex antigen?

T-dependent lymphopoiesis

what generates memory B cells from activated B cells?

class switching

what does T-dependent lymphopoiesis signal for?

go from producing IgM to IgG, IgA, and IgE

how do B cells class switch?

affinity of ABYs for antigen increases

what is the effect of affinity maturation of T-dependent lymphopoiesis?

Th and B cells need to interact

what needs to happen in order for a protein complex to be identified?

non-protein antigen

what protein antigen is less complex and can be identified without heavy influence from T cells?

T-independent antigen

what antigen does not require heavy influence from T cells?

B cell produces antibody

what happens to the B cell during T-independent lymphopoiesis?

T-indpendent has little/no class switching or affinity maturation; no memory cells produced

what are some differences between T-dependent lymphopoiesis and T-independent lymphopoiesis?

produce antibodies

what is the function of plasma cells?

bone marrow and secondary follicles

where are plasma cells located?

several days

what is the lifespan of plasma cells?

requires protein antigen

what do memory B cells require?

secondary follicles

where are memory B cells located?

they have the ability to respond rapidly and with greater intensity

what happens when memory B cells contact with antigen?

long life span

what is the life span of memory B cells?

injecting antigen to cause immunity by inducing a protective immune response against specific organism or its associated toxin prior to the encounter with the pathogen

what is immunization/vaccination?

protective acquired immune response

what does immunizations/vaccinations stimulate?

pathogen is killed by chemicals, heat, or radiation

what characterizes inactivated vaccines?

• safe

• do not require refrigeration

what are some advantages of inactivated vaccines?

weaker immune response/may require boosters

what is a disadvantage of inactivated vaccines?

• salk vaccine

• hepatitis A

what are some examples of whole virus inactivated vaccines?

pertussis

what is an example of a whole bacteria inactivated vaccine?

weakened by growing generations under modified hostile culture environment

how is an attenuated vaccine characterized?

retain antigenicity

what is an advantage of attenuated vaccines?

• has rare potential to revert to pathogenic form

• cannot be given to immunocompromised patients

what are some disadvantages of attenuated vaccines?

sabin

what is an example of an attenuated vaccine?

microbial polysaccharide antigens chemically coupled to proteins

what characterizes conjugate vaccines?

Haemophilus influenzae

what is an example of a conjugate vaccine?

• genetic sequence of a viral protein was copied into a yeast cell

• yeast cell was cultured, purified, and prepared into a vaccine

• viral surface protein is now detected by body

what are the steps to a synthetic vaccine?

Hepatitis B

what is an example of a synthetic vaccine?

uses microbe’s DNA or RNA that code for antigens

how is nucleic acid vaccines characterized?

• inexpensive

• easier production

• does not contain microbe

what are some advantages to nucleic acid vaccines?

• limited to distinct protein antigen

• genomic integration challenges

what are some disadvantages of nucleic acid vaccines?