Mucosal Immunity Flashcards
What is mucosal immunity? (2)
Cellular lining of the body
Forms the barrier between external and internal
What are the functions of the mucosal immune system? (3)
Maintain immune homeostasis at barrier sites while preserving physiological functions
What are the functions mucosal surfaces? (4)
Gas exchange (the lungs)
Food absorption (the gut)
Sensory activities (eyes, nose, mouse and throat)
Reproduction (uterus, vagina)
Describe the epithelium (5)
Lines mucosal surfaces defining the border between the environment and ourselves
Defends against invasion and absorption of unwanted toxins & pathogenic microbes
Selectively transports components essential for life to the lamina propria or systemic
circulation
Needs to distinguish harmful pathogens from harmless commensals
Doesn’t stop bacteria but prevents it from entering tissue
How do epithelial cells act as central organisers of the immune response (6)
Direct numerous components of the innate and adaptive immune systems at various levels including:
- barrier function
- processing and presentation of antigens
- expression of MHC and co-stimulatory molecules
- secretion of antimicrobial peptides
Epithelial cells secrete and respond to various mediators that profoundly affect the function of surrounding mucosal cell types
Importance of immunoglobulin A in mucosal immunity (3)
Presence of microbes in the gut elicits B-cell mediated IgA response. Their function includes:
- coating bacteria and modifying their ability to attach to mucosal surface of intestines
- Induce the expression of interleukin-10
Mucosa associated lymphoid tissue-MALT (4)
Umbrella term for organised lymphoid tissue at mucosal surfaces
Feature of all MALT is the absence of classical lymphatic structures
Has direct contact with overlaying epithelium
What is the mucosal immunity divided into? (2)
Inductive sites - organised MALT structures together with mucosa-draining lymph nodes
Effector sites - mucosa epithelia and the underlying lamina proprietor, which controls stomal cells and associated connective tissue stroma
Intenstina epithelial barrier (3)
Not a classical barrier but does inhibit bacteria from entering tissue
Specialised features that work to maintain a robust immune response to invading pathogenic microbes whilst tolerating commensal populations
Microfilm cells (2)
transport intact bacteria, abiotic particulates, and soluble antigens within vacuoles across their cell bodies
Isolated lymphoid follicles (4)
Develop after birth in response to antigen stimulation, by commensal bacteria
Contain many B cells and found in large intestines
Connect to draining lymph nodes
Called inductive sites because they are directly involved with antigen recognition
Host defence peptides (HDFs)
Antimicrobial peptides
Cationic peptides so disrupt bacterial membranes
Protect host cell from proteases, recruit can promote inflammation
Innate Lymphoid cells (4)
LC1, ILC2, and ILC3
Lack antigen specific receptors (No
BCR/TCR), but derive from the
common lymphoid progenitor
Although found in the blood in low
numbers, ILC are enriched in tissue and have a tendency for expansion at
barrier surfaces, including the gut, skin, and lung
Where are the ILCs predominantly found? (3)
ILC1 are found in the epithelial compartment
ILC2 are found in the lungs
ILC3 are found in the gut
Which ILC is important in asthma? (2)
ILC2:
promote recruitment, activation and survival of eosinophils
Augment mast cell degranulation and support immunoglobulin class switching to pro allergic igE antibodies
Which ILC is important in psoriasis? (2)
ILC3s act in conjunction with TH17 cells to promote neutrophil recruitment and hyper proliferation of skin epithelial cells
Which ILC is important in Chron’s disease? (2)
ILC1 - produce interferon gamma and activate epithelial so it becomes inflamed
Microbiome (3)
Commensal bacteria - ‘To eat at the same table’:
- Breakdown essential carbohydrates, produce vitamins
- Protection from pathogenic bacteria
Intestinal microbiota functions (4)
Biosynthetic functions
Immune maturation requires an intestinal microbiota:
- The microbiota facilitates the formation of Peyer’s patches and isolated lymphoid follicles and increases the recruitment of lymphocytes to the lamina propria
Metabolic functions
Protective functions
A ‘healthy’ microbiota is
protective against what? (4)
Clostridium Difficile Infection (CDI)
The microbiota can be disrupted
e.g. by antibiotics.
This allows C. difficile spores to germinate, grow, produce toxin and cause disease.
First line Treatment of CDI is with
antibiotics. This can lead to recurrences of disease
Immunomodulatory molecules in the gut (3)
Transforming growth factor beta - inhibitory cytokine
Retinoic acid
Interleukin 10 immunomodulatory cytokine
Toll signalling in the epithelium (4)
Activation of Toll-like receptor signalling in intestinal epithelial cells induces responses that modify intestinal crypt dynamics and IEC
functions to increase the integrity of the epithelial barrier
