C3 Neutrophils & macrophages

Question 1

what type of cells are neutrophils

Answer 1

PMN: polymorphonuclear leukocytes

produced by BM

Question 2

how do neutrophils die by apoptosis

Answer 2

Fas on surface & TNFR1 - bind to appropriate ligand activates MORT1 (FADD) & TRADD then activation of caspases

Question 3

name the main neutrophil cytokines
cytokines upregulated after stimulation
what pro-inflammatory responses
what anti-inflammatory reactions

Answer 3

TNFa & IL-8
IL-1, IL-8, IL-10, IL-12, IL-15, TNFa, IL-6 
IL-8, IL-6 & TNFa 
Resolvins & lipoxins 
Phagocytose target PRR important

Question 4

describe neutrophil recruitment

Answer 4

Roll along walls of post-capillary tubules
Respond to pathogen induced chemotactic signals (IL-8, GCP-2, LTB4)
Neutrophils move into tissues and out of vascular system (adhere to wall)
(Passing through the endothelial cell layer: extravasation/diapedesis)

Question 5

capture & rolling

what is tethering & rolling along blood vessel due to which molecule & name its types

Answer 5

Selectins: reversible binding of transmembrane glycoprotein adhesion molecules

1: leucocyte selectin = L-selectin (mel-14, LAM-1, CD62L) believed to bind to a fucosylated variant of CD34
2. Platelet selectin = P-selectin released onto outer surface of endothelial cells binds to PSGL-1 P-selectin glycoprotein ligand on neutrophil
3. Endothelial selectin = E-selectin (ELAM1; CD62) binds to a variety of sialic acid and fucose containing glycoproteins on neutrophil including: Sialyl Lewis X.

Question 6

firm adhesion is due to

Answer 6

1. Integrins: groups of heterodimeric transmembrane glycoproteins found on neutrophil mediate cell-cell or cell-extracellular matrix adhesion
   ▪ Macrophage antigen 1 = Mac1 (CD11b/CD18)
   ▪ Lymphocyte associated function antigen 1 = LFA1 (CD11a/CD18)
2. Intercellular adhesion molecules (ICAMs)
   ▪ Mac1 binds ICAM-1 preferentially on endothelial cells
   ▪ LFA1 binds ICAM-2 preferentially on endothelial cells

Question 7

describe Neutrophil homing to transmigration sites on endothelium

1. location
2. molecules involved
3. what does this lead to

Answer 7

location: tricellular junctions
2. PECAM1 (CD31) (located neutrophils & epithelial cells)
(can serve as its own ligand to form homodimers)
Has junctional location on endothelial cells so may serve as a homing device
3. Leads to extravasation (or diapedesis)

Question 8

describe transmigration

Answer 8

Little is known how neutrophils migrate through the sub-endothelial matrix.
May be:
helped by release of proteases.
CD18 also VLA (very late antigens) which bind fibronectin
laminin and other matrix proteins
VLA-4 also binds VCAM-1 which is expressed by fibroblasts and parenchymal tissues

Question 9

true or false TNFa & IL-1 are chemotactic

Answer 9

False - not chemotactic but can upreg adhesion molecules

Question 10

Name the 5 neutrophil receptors for chemoattractants

Answer 10

1. PAF (Platelet Activating Factor)
2. C5a
3. LTB4 (Leukotriene B4)
4. Formyl-methionyl-leucyl-phenylalanine
5. Chemokines – IL-8 plus 6 others identified (all w/ 4 cysteine residues)

Question 11

describe process of macrophage activation

Answer 11

monocytes for ~8hrs -> enter tissue & differentiate into macrophages
activity induced by stimuli (air pollutants, bacteria, viruses, cytokines)
Recognition of foreign material using —> PRR that interact with PAMPs

Question 12

describe what induces the type of macrophage

and describe two main types

Answer 12

Local environment e.g. for M1: LPS & IFNy.
For M2: IL-4 & IL-13 (TNF blocks)

M1: pro-inflammatory (IL-12, TNFa, IL-6, IL-1b, MCP-1)
Are classically activated
Target intracellular pathogens
- microbicidal, pathogen killing, tissue injury

M2: anti-inflammatory (TGFb, IL-10, MCP-1, TNFa, IL-6)
Are alternately activated
Target fungi & parasites, apoptotic cells, immune complexes & complement
- apoptotic cell clearance, high phagocytic capacity, wound healing

Question 13

Describe Chronic granulomatous disease (CGD)

Answer 13

Recessive X-linked disease
Mutations in gp91, p22, p47 or p67
A functional oxidase cannot be produced – patients have recurrent fungal or bacterial infections - showing importance of ability to produce an respiratory burst