Innate Immunity

Question 1

Which immunity is the first line defene against infection?

Answer 1

Innate immunity

Question 2

Name an obvious component of innate immune system

Answer 2

Skin

Question 3

Cells of innate immunity

Answer 3

• Antigen presenting cells (APCs), e.g. Dendritic cells, Macrophages
• Macrophages, Monocytes (Monocyte in blood matures in macrophage in tissues)
• Mast cells
• Granulocytes:
  
  • Neutrophils
  • Eosinophils
  • Basophils
• Complement proteins
• NK cells (Natural killer cells)

​So, most cells are from myeloid lineages (except NK cells and complement proteins)

Question 4

Cells that represent professional APCs

Answer 4

• Dendritic cells
• Macrophages

Question 5

Life course of macrophages

Answer 5

They originate from bone-marrow as ‘monocytes’ >>> remains in ‘blood and lymph’ as ‘monocytes’ >>> when exits lymphatic circulation and enters into tissues >>> differentiates into macrophages >>> so, in tissues, they remain as ‘macrophages

In short, monocytes (marrow, blood, lymph) >>> macrophages (tissue)

Question 6

What are the phagocytes? & where are they located?

Answer 6

Typically a resident macrophage

Phagocytic cells are located at the sites of invasion

(In acute inflammation, neutrophils are primary phagocytic cells)

Question 7

How do the phagocytes recognise infection or pathogen?

Answer 7

Uses >>> pattern-recognition receptors (e.g. toll-like receptors)

AND

Identifies >>> antigenic motifs >>> referred to as >>> PAMPs (Pathogen-associated molecular patterns)

Question 8

After recognition of pathogen by phagocytes >>>>> Next series of steps?

Answer 8

• Complement activation >>> to kill invading pathogen by MAC
• Chemokine release >>> to incease expression of adhesion molecule
• Cytokine release >>> to recruit adaptive immune cells

Question 9

What can happen after phagocytosis of a pathogen?

Answer 9

After phagocytosis of a pathogen >>> APC (Antigen presenting cells) can then express the pathogenic peptides on their cell surface >>> adaptive immune cells recognise the peptides

Question 10

Which are the principal cells to engulf bacteria?

Answer 10

Neutrophils (Polymorphonuclear leukocytes)

Question 11

What is the primary phagocytic cell in acute inflammation?

Answer 11

Neutrophil

Question 12

Neutrophil: properties

Answer 12

• The most common type of white blood cell
• It has multi-lobed nucleus - increases with age

Question 13

Neutrophil: granules

Answer 13

Neutrophil contains >>>

MPO (Myeloperoxidase)

Lysozyme

Question 14

Function of Neutrophils (PMNs) in innate immunity?

Answer 14

• Primary phagocytic cell in acute inflammation
• They engulf and then directly kill invading microorganisms
• Particularly active against bacteria
• Releases cytotoxic chemicals from granules
• Life span: minutes to days

Question 15

How do Neutrophils (PMNs) kill invading microorganisms?

Answer 15

They produce intracellular reactive oxygen species (using NADPH reductase) & lysozymes

Question 16

Eosinophils- are a type of?

Answer 16

Granulocytes (Granular cells)

Question 17

Role of eosinophils

Answer 17

• Important in ‘allergy’
• defence against ‘parasitic infection’ > protozoal and helminthic infections

Question 18

Basophil: Granules

Answer 18

Granules contain histamin and heparin

Question 19

Basophil: Functions

Answer 19

• During allergic response >>> releases histamine
• Expressess IgE receptor on the cell surface

Question 20

An important cause of Basophilia

Answer 20

CML (Chronic myeloid leukaemia)

It is unlikely to ever encounter an isolated basophilia outside the setting of a leukaemic process

Question 21

Mast cell: Granules

Answer 21

Granules contain histamin and heparin

Question 22

Mast cell: Functions

Answer 22

Similar to Basophil >>>

• During allergic response >>> releases histamine
• Expressess IgE receptor on the cell surface

​But thery are derived from different cell lines from Basophil

Question 23

Monocyte: Functions

Answer 23

• It differentiates into macrophage

Question 24

Macrophage: functions

Answer 24

• Involved in phagocytosis of cellular debris and pathogens
• Acts as an antigen presenting cell (APC)
• Major source of IL-1

Question 25

**What is 'foam cells'?**

Answer 25

**Fat-laden macrophages**

Question 26

**Dendritic cell: Functions**

Answer 26

**Act as APC (Antigen presenting cell)**

Question 27

**Type of WBC that are NOT part of innate immunity**

Answer 27

**Lymphocytes (B cells & T cells) \>\>\> they are the cells of adaptive immunity** **Regulatory lymphocytes & other lymphocytes \>\>\> they are the cells of adaptive immunity** **(Except, NK lymphocytes \>\> they are part of both innate & adaptive)**

Question 28

**Which cell of innate immunity does share features in common with adaptive immunity?**

Answer 28

**NK cells (Natural Killer Cells)**

Question 29

**What is NK cells?**

Answer 29

**Natural Killer cells** **A type of lymphocytes (lymphoid lineage cells)**

Question 30

**Role of NK cells (Natural Killer cells)**

Answer 30

* **They are able to recognise virally infected cells \>\>\> induce apoptosis** * **They also play a role in tumour surveillance \>\>\> induce apoptosis**

Question 31

**Granulocytes \>\> names**

Answer 31

* **Neutrophils** * **Eosinophils** * **Basophils**

Question 32

**Agranulocytes \>\> names**

Answer 32

* **Lymphocytes** * **Monocytes**

Question 33

**Nucleus of** **Neutrophil, Eosinophil, Basophil, lymphocyte, monocyte**

Answer 33

* **Neutrophil \>\>\> multi-lobed (3-5 segments)** * **Eosinophil \>\>\> Bi-lobed** * **Basophil \>\>\> Bi-lobed** * **Monocyte \>\>\> Kidney-shaped** * **Lymphocyte \>\>\> dense large (no lobe)**