Innate Immunity Flashcards
Which immunity is the first line defene against infection?
Innate immunity
Name an obvious component of innate immune system
Skin
Cells of innate immunity
- 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)
Cells that represent professional APCs
- Dendritic cells
- Macrophages
Life course of macrophages
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)
What are the phagocytes? & where are they located?
Typically a resident macrophage
Phagocytic cells are located at the sites of invasion
(In acute inflammation, neutrophils are primary phagocytic cells)
How do the phagocytes recognise infection or pathogen?
Uses >>> pattern-recognition receptors (e.g. toll-like receptors)
AND
Identifies >>> antigenic motifs >>> referred to as >>> PAMPs (Pathogen-associated molecular patterns)
After recognition of pathogen by phagocytes >>>>> Next series of steps?
- Complement activation >>> to kill invading pathogen by MAC
- Chemokine release >>> to incease expression of adhesion molecule
- Cytokine release >>> to recruit adaptive immune cells
What can happen after phagocytosis of a pathogen?
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
Which are the principal cells to engulf bacteria?
Neutrophils (Polymorphonuclear leukocytes)
What is the primary phagocytic cell in acute inflammation?
Neutrophil
Neutrophil: properties
- The most common type of white blood cell
- It has multi-lobed nucleus - increases with age
Neutrophil: granules
Neutrophil contains >>>
MPO (Myeloperoxidase)
Lysozyme
Function of Neutrophils (PMNs) in innate immunity?
- 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
How do Neutrophils (PMNs) kill invading microorganisms?
They produce intracellular reactive oxygen species (using NADPH reductase) & lysozymes
Eosinophils- are a type of?
Granulocytes (Granular cells)
Role of eosinophils
- Important in ‘allergy’
- defence against ‘parasitic infection’ > protozoal and helminthic infections
Basophil: Granules
Granules contain histamin and heparin
Basophil: Functions
- During allergic response >>> releases histamine
- Expressess IgE receptor on the cell surface
An important cause of Basophilia
CML (Chronic myeloid leukaemia)
It is unlikely to ever encounter an isolated basophilia outside the setting of a leukaemic process
Mast cell: Granules
Granules contain histamin and heparin
Mast cell: Functions
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
Monocyte: Functions
- It differentiates into macrophage
Macrophage: functions
- Involved in phagocytosis of cellular debris and pathogens
- Acts as an antigen presenting cell (APC)
- Major source of IL-1
What is ‘foam cells’?
Fat-laden macrophages
Dendritic cell: Functions
Act as APC (Antigen presenting cell)
Type of WBC that are NOT part of innate immunity
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)
Which cell of innate immunity does share features in common with adaptive immunity?
NK cells (Natural Killer Cells)
What is NK cells?
Natural Killer cells
A type of lymphocytes (lymphoid lineage cells)
Role of NK cells (Natural Killer cells)
- They are able to recognise virally infected cells >>> induce apoptosis
- They also play a role in tumour surveillance >>> induce apoptosis
Granulocytes >> names
- Neutrophils
- Eosinophils
- Basophils
Agranulocytes >> names
- Lymphocytes
- Monocytes
Nucleus of
Neutrophil, Eosinophil, Basophil, lymphocyte, monocyte
- Neutrophil >>> multi-lobed (3-5 segments)
- Eosinophil >>> Bi-lobed
- Basophil >>> Bi-lobed
- Monocyte >>> Kidney-shaped
- Lymphocyte >>> dense large (no lobe)
