Immunology Flashcards
Physiological function of mucosa tissues (4)
Gas exchange
Food absorption
Sensory activity
Reproduction
Lamina propria is filled with
Immune cells of all stages except neutrophils - Neutrophils only migrate to region during infection
Isolated lymphoid follicles produces
B cells
Peyer’s patches structure (3)
Covered by epithelial cells Contains M (Microvilli) cells with specialized membrane ruffles - Increases SA for absorption Underneath dome has dendritic cells, germinal centres and T cell centres
Immune action of M cells (3)
M cells take up antigen by endocytosis and phagocytosis
Antigen is transported across M cell in vesicles and released at basal surface
Antigen is bound by dendritic cells which activates T cells
Dendritic cells and epithelium layer
Can extend processes across epithelial layer to capture antigen from gut lumen
Integrin of mucosa epithelium
Alpha 4: Beta 7 integrin
T cell immune action (4)
Enters Peyer’s patches from blood vessels directed by receptors CCR7 and L-selectin
T cells encounter antigen transported across M cells and are activated by dendritic cells
Activated T cells drain to thoracic duct via lymph nodes and return to gut via bloodstream
Activated T cell expressing Alpha 4: Beta 7 integrin and CCR9 home to lamina propria and intestinal epithelium
Humoral Intestinal response ratios (4)
IgA - 80%
IgM - 15%
IgG - 5%
Systemic is opposite (GMA of same ratio)
IgA secretion (3)
IgA binds to poly-Ig receptor on basolateral face
Endocytosis and transcytosis to apical face
IgA dimer is released with secretory component - Broken down quickly with secretory component
IgA functions (3)
Neutralises pathogens and toxins on gut surface
Neutralises antigens internalized in endosomes
Exports toxins and pathogens from lamina propria
Intraepithelial lymphocytes - Special T cells (6)
90% of T cells with 80% CD8+
Activated appearance with killing machinery
Restricted antigen receptor repertoire
Expression of Alpha E: Beta 7 integrin anchors them in epithelium
2 types with different recognition mechanisms
Immunopathology coeliac disease
Intraepithelial lymphocyte (IEL) immune response (2)
Infection, toxins or damage causes secretion of gliadin peptide and displays CD8 IEL via MHC class 1 Activated IEL kills infected cell by perforin/granzyme and Fas-dependent pathways
Mechanisms of mucosal hyporesponsiveness (4)
Commensal organisms help regulate local hyporesponsiveness- PPAR gamma activation
Anergy or deletion of antigen specific T cells- No co-stimulation
Generation of regulatory T cells particularly CD4+ TGF Beta producing TH3 cells - Weak co-stimulation
(Both immunosuppressive and induces switching of B cells to IgA production)
Mucosal response to infection and regulation of mucosal immune responses (5)
Innate mechanisms eliminate most intestinal infections
Activation through pattern recognition receptors ligation
Intracellular sensors in epithelial cells, PRR, activate the NFkB pathway
Gene transcription and production of cytokines, chemokines and defensins
Activation of underlying immune response
Outcome of infection by intestinal pathogens is determined by
Complex interplay between the microorganism and the host I.R.
What happens when mucosal immunity becomes dysregulated in infectious disease (3)
Infection crosses mucosa and fuses to dendritic cells which shuttle virus to regional lymph nodes
Infection spreads to CD4+ lymphocytes
These viral infected cells go into bloodstream and disseminate across the body.
Selective IgA deficiency (3)
Asymptomatic
Recurrent sinopulmonary infections
Increases Coliac disease risk by 10 times
Common Variable Immuno-Deficiency (CVID) (3)
Recurrent sinopulmonary and GI infections
Failure to differentiate into Ig secreting cells
Low IgG,A,M,E
X-linked Agammaglobulinaemia (XLA) (2)
Sinopulmonary and GI infections with devastating systemic manifestations of chronic enteroviral infections
No B cells
Chronic Granulomatous Disease (CGD) (2)
Staph. aureus/Inflammatory granulamos-pneumonia, liver abscess, perianal abscess and skin abscess
Failure of phagocyte respiratory burst
SCID (3)
Profound defect in T and B cell immunity
Causes oral candidiasis, Chronic diarrhoea, Interstitial pneumonitis
Pathogens commonly involved are EBV and rotavirus
Food allergy (3)
Type I hypersensitivity
IgE secreted by plasma cells forms crosslink on mast cell surface
This secretes signals to B cells triggering more IgE production
Memory response- immune system must be primed
Coeliac Disease/ Gluten sensitive enteropathy (6)
Genetic disease to HLADQ2/HLADQ8 (MHC class 2 molecules)
NOT an allergy
Trigger is enteric viruses
Gamma interferon from Gluten specific T cell activate epithelial cells which produce IL-15 inducing proliferation and activation of IEL
Diagnosed by biopsy (GOLD STANDARD) and serology (looks for IgA auto antibodies with 95% clinical sensitivity)
Gluten must be consumed prior to testing for antibodies to be present
