B3.039 - Prework Immune Cell Development Flashcards
what are naive lymphocytes
lymphocytes that express antigen receptors but cant do anything
where do naive lymphocytes circulate and what do they do
amongst peripheral lymphoid organs surveilling for antigens
when do naive lymphocytes differentiate?
upon exposure to memory or effector cells
how do naive lymphocytes die
undergo apoptosis if they dont find their antigen within weeks to months
B cell effector cells do what
produce molecules that eliminate antigens
what do plasma cells do
produce antibodies in the peripheral lymphoid tissues
what do plasmablasts do
produce antibodies in blood stream
what do T cell effector cells do
produce molecules that eliminate antigens
CD4+ T helper cells do what
produce cytokines to activate B cells, macrophages and others
what do CD8+ T cytotoxic cells do
kill infected host cells
what is a lymph node
encapsulated aggregates of lymphoid tissue
what do lymphatic vessels carry
lymph that has drained from tissues to lymph nodes
Describe the role of APCs and lymph
APCs sample lymph for antigens to microbes
what do dendritic cells do with regards to lymph
dendritic cells capture antigens of microbes and transport hem to lymph node via the afferent lymphatic vessel
What is in the follicles of lymph nodes
B cells - periphery/cortex
Follicular dendritic cells
What is in the germinal center of a lymph follicle
B cells that have recently responded to an antigen
Site of antibody production
what is the site of antibody production
germinal center of follicle
What is in the paracortex of lymph nodes
T cells adjacent to the follicles
Dendtritic cells
where do naive T and B lymphocytes enter through
HEV high endothelial venule
what is the receptor on B cells that homes them to the follicle
CXCR5
what is the receptor that homes T cells to the paractorex
CCR7
plasma cells secrete what
antibodies into the blood stream and onto mucosal surfaces to bind microbes or their toxins
do plasma cells migrate to sites of infection
no
to effector T cells migrate to sites of infection
yes
what do non effector T memory T cells do
recirculated in the lymph node
in the spleen pathogens are coated by antibodies generated from where
the white pulp
what does the red pulp do
filters and removes microorganisms via phagocytes as well as old RBCs
what is PALS
periarteriolar lymphoid sheath that surrounds the splenic arteriole
what is the white pulp made of
PALS and lymphoid follicles together
what surrounds the white pulp
the red pulp
what is the mantle zone of the spleen
ring of lymphocytes surrounding the germinal center
what is the marginal zone
interface between the red pulp and white pulp where particulate antigen from circulation is trapped and presented to APCs
what constitutes GALT
spleen
lymph nodes
what is the function of GALT
trap pathogens and their secreted antigens that have entered through the GI tract
Presentation to naive lymphocytes passing through
what do M cells do in the GALT
they are specialized epithelial cells that promote antigen transportation to underlying tissues
what type of cells find antigen in the lamina propria and activate innate and adaptive immunity
dendritic
T cells
macrophages
what are peyers patches
organized areas of lymphoid aggregates
what antibody transports to the lumen to neutralize microbes
IgA
what keeps T lymphocytes from attacking commensal microbes in the GALT/MALT and cutaneous lymphoid tissue
T regulatory cells and others
what percentage of lymphocytes are in the GALT/MALT and cutaneous lymphoid tissue
25%
the cortex of the thymus has what kind of cell
immature T lymphocytes that differentiate, undergo selection
what type of cell is in the medulla
less T lymphocytes
undergo further selection and mature prior to leaving
what are hassals corpuscles
within the medulla
flat keratinized degenrate epithelial cells
What is the order of IgH rearrangement
- D to J recombination
- V to DJ
- V(D)J recombinase - a group of enzymes that mediate recombination
what are lymphocytes specific enzymes of recombination
RAG-1 and RAG-2
TdT
what are ubiquitously expressed enzymes for IgH rearrangement
DNA ligase IV and DNA-PK
what do RAG1/2 mediate
combinatorial diversity
what is mediated by TdT
Junctional diversity
What is junctional diversity created by
addition/subtraction of nucleotides at the coding joint
Autospecific B cells undergo what before destruction
a second kappa/lambda locus rearrangement
L chain gets replaced and then goes through selection again
what is negative selection
if BCR editing doesnt succeed, undergo apoptosis
Most immature B cells die
what is positive selection
becoming mature naive B cells
what do most mature naive B cells express
IgM and IgD
what do pro B cells express
RAG-1/2, TdT
what do Pre B cells express
IgM and surrogate light chain
Re express RAG1/2
what do immature B cells express
IgM and kappa or lambda light chain
what do mature B cells express
IgM and IgD (most co express)
what are TRECs
T cell receptor excision circles
what do TRECs do
they are circular DNA formed by genomic rearrangement that occur during VDJ recombination
what is the diagnostic usage of TRECs (qPCR)
newborn screening for immunodeficiency
Thymic output after HSCT
What does having TRECs tell you
you have activated T cell receptors leaving the thymus
What is a DN thymocyte
analogous to Pro and Pre B cells
what is expressed by DN thymocytes
Pre TCR
what is a DP thymocyte analogous to
immature B cell
what is expressed by DP thymocyte
TCR alpha beta, CD4, CD8
what are SP thymocytes analagous to
mature B cells
how does positive selection for T cells work
TCR binds MHC peptide complexes in the thymus, only cells expressing a TCR that can bind MHC peptide can be positively selected
what determines if a T cell will differentiate into CD4 or CD8
if the DP CD4/8+ expresses a TCR that recognizes MHC Class 1 then its CD8 and vice versa
how does negative selection for T cells work
cells that fail to bind undergo apoptosis
