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Lecture 1
Lecture 1 - Cells and Tissues of the Immune Response
47
Medical
Professional
08/17/2009

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Term
Describe naive B and T cells.
Definition

have not interacted with antigen

small

motile

nonphagocytic cells

- enter the LN via an artery, enter the stroma of LN through HEV

Term
What are Natural Killer Cells?
Definition

large granular lymphocytes

part of innate immune system

recognize tumor or virus-infected cells despite no antigen-specific receptors

do not have TCR or Ig in plasma membranes CD16+

Term
Describe the morphology of unactivated B and T cells.
Definition
  • remain in G0 phase of cell cycle
  • 6um in diameter
  • cytoplasm forms rim around nucleus
Term
Describe effector cells
Definition
  • eliminate antigen life span from few days to few weeks include:
    • Th cells (cytokine secreting)
    • Tc cells (antigen-activated)
    • mature cells
Term
What do memory cells do?
Definition
  • responsible for lifelong immunity to many pathogens
  • look like small lymphocytes
Term

ADCC

 

Definition

(antibody-dependent cell-mediated cytotoxicity)

NK cells attach to CD16 antibodies and destory targeted cells

Term

What are mononuclear phagocytes?

Where do they arise?

What receptors do they possess?

What stages of development do they go through?

Definition

phagocytic cells that ingest particulate antigens and enzymatically degrade them within their lysosomal compartments

  • arise from progenitor cells in bone marrow
  • possess receptors for the Fc portion of IgG molecules
  • possess receptors for some components of Complement
  • progress: monoblasts -> promonocyte -> monocyte -> macrophage
Term
describe monocytes
Definition
  • smaller than macrophages
  • less organelles
  • circulate in bloodstream for about 8 hours, get bigger and migrate to tissues and become macrophages
  • 5-10% of peripheral blood mononuclear cells
  • leave blood and accumulate at inflammatory sites
  • respond to chemotactic stimuli
  • generally do NOT reenter the circulating pool
Term
Macrophages in different places are called?
Definition
  1. gut = intestinal macs
  2. lung = alveolar macs
  3. connective tissues = histiocytes
  4. liver = kupffer cells
  5. kidney = mesangial cells
  6. brain = microglial cells
  7. bone = osteoclasts
Term
What is extravasation? What are the steps?
Definition

movement of circulating neutrophils into tissues

1) cell adheres to vascular endothelium

2) penetrates gap between adjacent endo cells lining vessel wall

3) penetrates vascular basement membrane

4) moves into tissue spaces

Term
What are HEVs and what do they do?
Definition

high endothelial venules:

  • sites where lymphocytes leave blood stream and enter lymphoid tissue
  • most lymphocytes that eneter at node arrive by passing btwn specialized endothelial cells of the HEV by extravasation
  • lymphocytes express surface receptors that bind to molecules present on the outer membrane of HEV
Term
Where/What is the red pulp?
Definition
  • spleen
  • network of sinusoids populated by macrophages, numerous red blood cells and few lymphocytes where old and defective RBCs are destroyed and removed
  • many macrophages within the red pulp contain engulfed RBCs or iron containing pigments from degraded hemoglobin
Term
Where/What is the white pulp?
Definition
  • spleen
  • surrounds the branches of splenic artery, forming PALS (periarteriolar lymphoid sheath)
  • populated mainly by T lymphocytes
  • primary lymphoid follicles are attached to PALS follicles and are rich in B cells and some contain germinal centers
Term
Where/what is the marginal zone?
Definition
  • spleen
  • peripheral to PALS is populated by lymphocytes and macrophages;
  • antigen is trapped by dendritic cells which carry it to the PALS.
  • lymphocytes in the blood also enter sinuses in the marginal zone and migrate to the PALS
Term
What are the effects of a splenectomy on kids and adults?
Definition

in children - increases bacterial sepsis:

streptococcus pneumoniae

neisseria meningitidis

Haemophilus influenzae

in adults - bacteremia

Term
What are totipotent cells?
Definition
can give rise to an entire organism; a fertilized egg is totipotent.
Term
What are pluripotent cells?
Definition
arise from totipotent cells, and can give rise to most but not all of the cell types necessary for fetal development. cannot generate a placenta. aka embryonic stem cells (es cells) can be isolated from early embryos
Term
What are multipotent cells?
Definition
give rise to only a limited # of cell types
Term
What can unipotent cells generate?
Definition
can generate only the same cell type as themselves
Term
Name the primary lymphoid organs?
Definition
  1. thymus (where T cells learn to recognize self and non-self)
  2. bone marrow
Term
Name the Secondary Lymphoid Organs
Definition
  1. Spleen
  2. Lymph Node
  3. MALT
Term
Describe a B lymphocyte.
Definition
  • bone-marrow derived cells capable of producing Ab
  • mature B cells represent 10-15% of circulating lymphoid pool
  • majority express IgM and IgD
  • Differentiate into Ab-producing plasma cells following stimulation with antigen
Term
Describe a T lymphocyte.
Definition
  • all express TCR for antigen derived from lymphoid progenitor in BM
  • differentiate/mature in the thymus
Term
What are the markers for a Treg and what do they do?
Definition
  • CD4+ and CD25+
  • negative regulators of the immune system
Term
What are APCs?
Definition
Antigen Presenting Cells - capture antigens display antigen to lymphocytes and provide signals that stimulate proliferation and differentiation of lymphocytes
Term
Name 2 kinds of mononuclear phagocytes.
Definition
  1. monocytes
  2. macrophages
Term
What do macrophages do? (basic version)
Definition
  • phagocytic function
  • secretory function:
    • produce several cytokines
  • various roles in immune responses:
    • initiation (antigen processing and presentation)
    • regulation (enhancement/suppression)
    • effector function (cytokine production; cytotoxicity)
Term
What are DCs and what do they do? basic idea
Definition
  • Dendritic Cells
  • accessory cells that participate in immune response: 

1) present in interstitium of most organs; abundant in T cell-rich areas of lymph nodes and spleen

2) scattered throughout the epidermis of skin

3) arise from bone marrow precursors, and are derived from monocyte lineage precursors

4) very efficient APC for T cell responses to protein antigens

Term
What are Follicular Dendritic Cells (FDCs) and are they related to DCs?
Definition

1) present in germinal centers of lymphoid follicels in LN, spleen and MALT

2) NOT derived from BM precursors; unrelated to DCs that present antigens to T cells

3) trap antigens that are complexed to antibodies (immune complexes) or complement

4) act as APCs for B cells

Term
Where do B cells reside in LNs?
Definition
outer cortex - aggregated in lymphoid follicles with germinal centers
Term
Where do T cells reside in LNs?
Definition
mostly CD4+ predominantly beneath and between the follicular areas (aka parafollicular cortex)
Term
Where are the T cells and B cells in the LN?  name the regions.
Definition
[image]
Term
What is the purpose of CCR7, and what cells express the receptor?
Definition

Cells expressing receptor:

  • T lymphocytes
  • Dendritic Cells
  1. These cells exhibit chemokine-directed migration patterns
  2. CCR7-binding chemokines are produced in T cell zones, and attract naive T cells and Dendritic Cells into these areas of the LN
Term
What is the purpose of CXCR5 and what cell expresses it?
Definition
  • naive B cells express CXCR5
  • CXCR5 only recognizes a chemokine produced in follicles
  • B cells are therefore attracted to the B cell zones of LN.
Term
Where are dendritic cells found in LN?
Definition
T cell zones
Term
Where are Follicular Dendritic cells found in LN?
Definition
in germinal centers
Term
What does the spleen do? (immune and non-immune)
Definition
  1. site of hematopoiesis
  2. site of cell-cell interactions for immune responses against blood-borne antigens.
Term
What are PALS?
Definition
  • Periarteriolar lymphoid sheaths
  • small arterioles surrounded by lymphocytes
  • T cells predominate
  • B cells are in follices and germinal centers taht are attached to the T cell zones
Term
What is a Langerhan Cell, and what part of the immune system does it belong to?
Definition
  • immature dendritic cell of the cutaneous immune system
  • form a continuous epidermal meshwork
  • captrue antigen and migrate to draining LN where they act as APCs
Term
What is MALT?
Definition
  • Mucosa associated lymphoid tissue
  • aggregates of lymphocytes, macrophages, DCs

located in 3 main areas:

  1. within epithelial layer (CD8+)
  2. throughout lamina propria (activated CD4+, activated B cells, plasma cells)
  3. Peyer's patches (B cell follicles and germinal centers, small #CD4+)
Term
What is the recirculation pathway of naive lymphocytes?
Definition
recirculate through peripheral lymphoid organs
Term
What is the recirculation pathway of effector lymphocytes?
Definition
migrate to various tissues at sites of infection and inflammation
Term
What are some B cell markers?
Definition
  1. CD5
  2. CD19
  3. CD20
  4. CR2 (CD21)
  5. CD32 (Fcy-RII)
  6. CR1 (CD35)
  7. CD40
  8. CD72
  9. Igbeta
  10. Igalpha
  11. sIg
  12. MHC I
  13. MHC II
  14. ME-R
Term
What are some makers of T cells?
Definition
  1. CD2
  2. CD3
  3. CD4
  4. CD5
  5. CD7
  6. CD8
  7. CD28
  8. TCR
  9. MHC I or II
Term
What do Th cells do?
Definition

SECRETE CYTOKINE

this can cause:

1) activation of macrophages

2)inflammation

3)activation of T and B lymphocytes

Term
What do CTLs do?
Definition
kill the infected cell
Term
What are the markers of monocytes/macrophages?
Definition
  1. MHC I
  2. CD64 (Fcy-RI)
  3. CD32 (Fcy-RII)
  4. CD16 (Fcy-RIII)
  5. MHC II
  6. CD35 (CR1)
  7. CD11b (CR3)
  8. CD11a (LFA-1)
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