Immunology exam III

what are monoclonal antibodies produced by

Single B cell clone

what is one of the most important technological advances in immunology

Monoclonal Antibodies

when do B cells have a short life span

in vitro

what happens to B cells when they are fused with Myeloma cells

become immortal

what is a myeloma cell

plasma cell tumor

B cells can be harvested from what

animal immunized with antigen

Myeloma cells can be engineered to lack what

enzymes

what enzymes can be removed from myeloma cells

Thymidine Kinase (TK)

Hypoxanthine-guanine phosphoribosyl transferase (HGPRT)

what is a de novo pathway

the synthesis of a molecule from scratch

what do myeloma cells rely on to survive

de novo pathway of nucleotide biosynthesis

if the de novo pathway of nucleotide biosynthesis is blocked, what would happen to myeloma cells

death

how do fused cells (hybridomas) survive

either salvage or de novo pathways

what provides the missing enzymes for myeloma cells

B cells

when do B cells need to provide the enzymes for myelomas

salvage pathway

unfused myeloma cells rely on what pathway and what happens to B cells

unfused myeloma cells rely on de novo pathway, B cells will die

what does the HAT medium do

selects immortalized hybridoma cells by blocking de novo pathway

what does HAT stand for

Hypoxanthine

Aminopterin

Thymine

what does Hypoxanthine do ( what is it used for)

Purine substrate for HGPRT → salvage pathway

what is aminopterin used for

blocks tetrahydrofolate (THF) reductase, which is necessary for de novo DNA synthesis

what is thymine used for ( where is it used )

pyrimidine substrate for TK → for salvage pathway

what are homogenous mAbs

Igs derived from a single B cell clone

mAbs are made for what

any antigen

how are most mAbs made

fusing cells from immunized mice with mouse myelomas

can Murine mAbs be injected into humans- explain

No- human immune system sees the mouse Ig as foreign- immune response begins

what mAbs are the most suitable for humans

humanized mAbs

how can genetic engineering help mouse mAb bind

Igs can retain Ag-binding V regions of mouse mAb within human skeleton

what can prolonged use of humanized mAbs elicit

anti-Ig Igs (against the mouse Ag-binding regions)

what can mAbs be used for

therapeutic and diagnostic agents for many diseases

what is a TCR made out of

membrane bound heterodimer

alpha and beta chains

what do TCRs recognize

peptide-MHC complexes

what are TCRs analogous to

Ig Fab

what is TCR beta analogous to

end of Ig heavy chain

what is TCR alpha analogous to

Ig light chain

what two regions does a TCR contain

V and C region

how many CDRs in V region of TCR

3

TCR V and C regions are homologous to what

Ig V and C regions

can TCRs transmit signals to the T cell on its own

no

are TCRs secreted

No

always membrane bound

do TCRs undergo affinity maturation

No

what is responsible for signaling when TCRs recognize Ags

CD3 and zeta proteins that are linked to the TCR

CD4 and CD8 are what type of molecules

coreceptor molecules

what do CD4 or CD8 do

recognize non-polymorphic regions of MHC molecules

also transmit signals

Igs often to bind to chemical strucutres with what affinity

high affinities

where might microbes and toxins be present in low concentrations

circulation

lumens of mucosal organs

TCRs only bind MHC-peptide complexes with what affinity

low affinity

what do adhesion molecules do for T cells

strengthen the binding of T Cells to APCs

TCR 3D structure is similar to Ig Fab, but how does it differ from Igs

TCR a/b chains are anchored in plasma membrane

TCRs are never secreted

TCRs do NOT undergo isotype switching or affinity maturation

% of cells with gamma delta TCRs

5-10%

what do gamma delta TCRs recognize

variety of protein and non protein Ags that are usually not displayed by classical MHC molecules

where are gamma delta TCRs abundant

epithelia

how is the specificity and function of gamma delta TCRs

not well established

when do lymphocyte clones arise

before encounter with Ags

True or False: there are not enough genes in the human genome for every possible receptor to be encoded by a different gene

true

are molecular processes influenced by what receptors recognize

NO

when does recognition occur with lymphocyte maturation

after receptor generation and expression

what does lymphocyte maturation expression lead to

selection process

what does the selection process of lymphocyte maturation promote and eliminate

promotes survival of cells with function Ag receptors

eliminates cells that cannot recognize Ag or cells that cause harm

stem cell that lymphocytes come from

hematopoietic stem cell

positive selection of lymphocyte development

weak recognition of self Ags

preserves and expands cells that express potentially useful Ag receptors

Negative selection of lymphocyte development

strong recognition of self Ags

triggers apoptosis

deletes cells that are potentially harmful to self

what does somatic V gene recombination form

functional genes that encode B and T cell receptors

Ig HC and LC loci and TCR a and b chain loci contain how many V and C regions

both contain multiple V regions (30-50)

and one or a few C regions

what exists between V and C regions

several short coding sequences

what do Joining gene segments do

encoding for C-terminal portions of the V domain

where do Diversity gene segments exist

between the V and J segments in the Ig heavy chain and TCR beta loci

VDJ recombination = ?

Somatic DNA recombination

what happens with the Ig HC gene segments in Pro-B cells

randomly recombine

one D gene with one J

One V with the fused DJ

combination of LC loci

same as pro-b cell

lack D segments

V and J combine

combination of TCR beta chain genes

analogous to Ig HC

VDJ combination

Combination of TCR alpha chain genes

analogous to Ig LC

VJ combination

what is VDJ recombinase (VDJase)

lymphoid specific enzyme

mediates somatic V(D)J recombination in immature B and T cells

What does VDJase recognize

recognizes DNA sequences that flank all Ig/TCR V, D, and J genes

what do DNA ligases repair

repair dsDNA breaks introduced by VDJase

expression of lineage-specific transcription factors determine what

lineage specificity of Ig vs. TCR receptor genes

how is diversity of Ag receptors achieved

combinatorial diversity

junction diversity

what is combinatorial diversity

random combinations of V, D, and J genes in different lymphocyte clones

limited by the number of V D and J genes

what is junctional diversity

random change of nucleotides at V(D)J junction

almost unlimited

generates more random DNA sequence changes than can be generated by recombination of V-D-J genes in the germline

Breaks in DNA from V(D)J is randomly edited by what before final repair

Terminal deoxyribonucleotidyl transferase (TdT)

what can repairs with TdT result in

nucleotide deletions, addition, and mutations

may produce non-functional genes

why are lymphocyte checkpoints needed

ensure only functional cells with functional receptors survive

what are CDR3 loops encoded by

DJ segments and junctional sequences

pre-b cells are defined by what protein expression

Ig mu

what is in the pre-BCR complex

Ig mu'

two invariant surrogate light chains

Ig a and IG b signaling molecules

the pre-BCR complex signals/promotes what which results in what

promotes survival and proliferation

results in first checkpoint in B cell development

when is lambda LC produced

only if rearranged k LC locus fails to express a functional k protein

what cell is associated with the second checkpoint during the maturation of B cells

immature B cells

what is allelic exclusion

pre-BCR complex signals shut off

recombination of Ig HC and LC genes on the second chromosome when HC/LC are productive

what does allelic exclusion ensure

ensures each cell can only express a receptor of a single specificity

what do B cells produce from one of the inherited parental alleles

one Ig mu

one k or lambda chain

two sets of inherited LC and HC genes increases the change of what

successful gene recombination and receptor expression

what is positive expression of B cells based on

expression of complete BCRs no on Ag recognition specificity

what Igs help B cells further in BM or spleen

IgD

IgM

where do mature B cells go

peripheral lymphoid tissues

what is negative selection triggered by

high affinity binding by immature B cells to ubiquitous self antigens

what is receptor editing

inactivates/eliminates k chain genes that generate a potentially harmful self-reactive receptor

via re-expression of the VDJase

why is T cell maturation unique

different subsets of T cells are specific for certain classes of MHC molecules with peptides displayed

the least developed T cell progenitor that migrate from BM to thymus

Pro-T cells

(double-negative T cells)

what do pro-T cells NOT express

CD4

CD8

Pro-T cells proliferate under the influence of what

IL-7 that is produced in thymus

Pre-T cells express what

functional Pre-TCR complex

TCR b chain expressed on cell surface with invariant protein called pre-T a