have not interacted with antigen

small

motile

nonphagocytic cells

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

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+

• remain in G0 phase of cell cycle
• 6um in diameter
• cytoplasm forms rim around nucleus

• eliminate antigen life span from few days to few weeks include:
  
  • Th cells (cytokine secreting)
  • Tc cells (antigen-activated)
  • mature cells

• responsible for lifelong immunity to many pathogens
• look like small lymphocytes

ADCC

(antibody-dependent cell-mediated cytotoxicity)

NK cells attach to CD16 antibodies and destory targeted cells

What are mononuclear phagocytes?

Where do they arise?

What receptors do they possess?

What stages of development do they go through?

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

• 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

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

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

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

• 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

• 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

• 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

in children - increases bacterial sepsis:

streptococcus pneumoniae

neisseria meningitidis

Haemophilus influenzae

in adults - bacteremia

1. thymus (where T cells learn to recognize self and non-self)
2. bone marrow

1. Spleen
2. Lymph Node
3. MALT

• 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

• all express TCR for antigen derived from lymphoid progenitor in BM
• differentiate/mature in the thymus

• CD4+ and CD25+
• negative regulators of the immune system

1. monocytes
2. macrophages

• 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)

• 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

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

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

• 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.

1. site of hematopoiesis
2. site of cell-cell interactions for immune responses against blood-borne antigens.

• 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

• 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

• 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+)

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

1. CD2
2. CD3
3. CD4
4. CD5
5. CD7
6. CD8
7. CD28
8. TCR
9. MHC I or II

SECRETE CYTOKINE

this can cause:

1) activation of macrophages

2)inflammation

3)activation of T and B lymphocytes

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)