IS Lymphocytes and Lymphoid Organs Flashcards
- primary cell involved in the immune response
- matures in the primary lymphoid organs
Lymphocytes
?% of circulating WBCs does lymphocytes represent
20-40%
size of lymphocytes?
7-10 um
round; large, w/ dense chromatin that stains deep blue
Nucleus
sparse, few organelles, no specific granules, light blue staining
Cytoplasm
what are the primary lymphoid organs?
Bone Marrow and Thymus
- primary site of hematopoiesis
- site of B cell development
- main source of HSCs
Bone Marrow
- found in the thorax, inferior to the thyroid gland and anterior to the heart
- site of T cell development
Thymus
- where lymphocytes spends most of its lifespan
- sites of antigen-dependent lymphopoiesis
Secondary Lymphoid Organs
- indiscriminate filter of the blood
- largest secondary lymphoid organ
Spleen
where is the spleen located?
Upper left quadrant of the abdomen
graveyard of old and dying RBCs
Red Pulp
contains lymphoid tissues arranged around arterioles in a periarteriolar lymphoid sheath (PALS)
White Pulp
- Main function: filtration
- central collecting points for lymph fluid from adjacent tissues
- located along lymphatic ducts
Lymph Nodes
main function of lymph nodes?
Filtration
found in gastrointestinal, respiratory, and urogenital tracts
Mucosa-associated lymphoid tissue (MALT)
responds to pathogens entering the respiratory and alimentary tracts
Tonsils
association of intra-epidermal lymphocytes (mostly T cells)
Cutaneous-associated lymphoid tissue
antigen contact in the lymph nodes leads to lymphocyte proliferation and activation of other cells, causing lymphadenitis
Lymphadenopathy
- rearrangement of genes that code for the heavy & light chains
- antigen-independent phase
Pro-B cell
what chromosome?
heavy chain
Chromosome 14
what chromosome?
light chain
Chromosome 2 and 22
systhesis of heavy chain in?
cytoplasm
expresses μ heavy chain associated with 2 “surrogate light chains”
Pre-B cell
- complete IgM on cell surface
- self-antigens send a negative signal to these cells
- self-reactive cells are destroyed by apoptosis
Immature b cell
what kind of signal is sent to the cells by self-antigens?
Negative
rearrangement of genes in either what chromosome?
Chromosome 2 or 22
- they mature as marginal zone B cells or follicular B cells
- expresses IgD
Mature Naive B cell
marginal zone B cells reamin where?
Spleen
migrates to lymph nodes and other lymphoid organs
Follicular B cells
where does follicular B cells migrate?
lymph nodes and other lymphoid organs
- spherical or ellipsoidal cells
- eccentric nucleus, heavily clumped chromatin
- found either in the bone marrow or germinal centers
Plasma cells
produce cytokines allowing plasma cells to be long-lived
Stromal cells in Bone Marrow
size of plasma cells
10-20 um
B cell development
- Pro B cell
- Pre B cell
- Immature B cell
- Mature B cell
- Activated B cell
- Plasma cell
Stages of T cell differentiation
- Double negative Thymocyte
- Double Positive Thymocyte
- Single Positive Thymocyte
- Mature Naive T cells
- Activated T cells
- actively proliferate in the outer cortex under the influence of IL-7
- rearrangement of TCR gene begins here
Double-negative thymocytes
thymocytes lack?
CD4 and CD8
- express both CD4 and CD8 surface markers
- rearrangement of alpha chain genes begin here
Double-positive thymocytes
thymocytes with functional TCR-CD3 complex will be allowed to survive
Positive Selection
selection of thymocytes that will interact with host cell MHC molecules
MHC Selection
- only 1-3% of thymocytes survive here
- negative selection and clonal deletion occurs here
Single-positive thymocytes
thymocytes with strong reactions with self-peptides other than MHC antigens are eliminated through apoptosis
Negative selection
the process of eliminating clones of T cells that is capable of an autoimmune response
Clonal deletion
?% of thymocytes survive?
1-3%
- exhibit only 1 type of marker (CD4 or CD8).
- have a lifespan of several years
Mature naive T cells
mature naive T cells exhibit only 1 type of marker ? or ?
CD4 or CD8
mature naive T cells reticulates every?
12-24 hours
CD4+ T cells (T helper cells) reacts wt?
MHC class II
CD8+ T cells (T cytotoxic cells) reacts wt?
MHC class I
Heterodimer of two polypeptide chain (alpha and beta) covalently bonded by disulfide bonds
T Cell Receptor
heterodimer of 2 polypeptide chain by T cell receptor are?
Alpha and Beta Chain
T cell receptor are expressed by both?
CD4 and CD8
rearrangement of beta chain?
Chromosome 7
rearrangement of alpha chain?
Chromosome 14
group of proteins that are physically associated with TCR?
CD3 complex
consists of a delta chain, gamma chain, zeta chains
CD3 complex
ensures cell surface expression of TCR
CD3 complex
3 types of chains that consists of CD3 complex
Delta chain, Gamma chain, Zeta chains
presenting antigens from intracellular pathogens
MHC class I molecule
presenting antigens from extracellular pathogens
MHC class II molecule
proliferate and produce cytokines
CD4 T cells
- antigen specific
- bind and kill infected cells by inducing apoptosis
CD8 T cells
2 signals that B cell requires
- Ag-sIg crosslinking
- B cell-Th cell binding through TCR and CD40 (B) and CD40L (T)
- activated B cells express CD25 (for IL-2)
- migrates either to T cell zone or B cell follicles
- leads to formation of plasma cells and memory B cells
Responses to TC-dependent antigens
- elicits antibody formation in the absence of T cell help
- produces IgM only
- almost no production of memory B cells
Responses to TC-independent antigens
antibody kinetics to TC dependent antigens phases?
- Lag/Inductive/Latent
- Log/Exponential
- Plateau/Steady-state
- Decline/Decay
- gold standard in identifying lymphocytes
- uses labeled monoclonal antibodies against surface markers
Flow Cytometry
CD2, CD3, CD4, CD8
T cells
CD19, CD21, CD22, sIg
B cells
activates cytotoxic lymphocytes and macrophages
Th1
help B cells produce antibodies
Th2
produces IL-9 (proinflammatory)
Th9
produces IL-17 and IL-22 (increase inflammation and joint destruction).
Th17
suppresses immune responses to self-antigens.
T regulatory cell (Treg)