Block 1 Flashcards
pathogen sizes small-large
viruses, bacteria, fungi, protozoa, worms
phagocytes
2-8% of WBC: monocytes, macrophages, dendritic cells
Eats stuff
granulocytes
neutrophils=40-60%
eosinophils=1-4%
basophils and mast cells=0.5-1%
release toxic compounds
natural killer cells
2-3% of WBC
type of lymphocyte
kill virally infected cells and tumour cells
CD8+ cytotoxic T cells
20% of WBC
kill virally infected cells, tumour cells and allografts
CD4+ helper T cells
45% of WBC
Th1, Th2, TH9, TH17, regulatory T cells (Treg)
Help other cells by releasing cytokines
Regulate immune responses
Gamma delta T cells
5% WBC
immunoregulatory and cytotoxic
B cells
23% WBC
make antibodies
complement pathways
classical, alternative, lectin
what do the complement pathways result in
-phagocytosis by opsonising antigens
-inflammation by attracting macrophages and neutrophils
-membrane attack by rupturing cell wall of bacteria to lyse cells
what are cytokines
hormone-like secreted proteins that act through cell surface receptors
what do cytokines include
chemokines, interferons, interleukins, lymphokines and tumour necrosis factors
what are antibodies (Ig)
large Y-shaped proteins produced by plasma B cells that specifically recognise pathogen epitopes
main functions of antibodies
neutralisation, aggulation, complement
what do PAMPS bind to in the innate immune system
patter recognition receptors (PRRs)
classical complement pathway
antigen: antibody complexes activated =>recruitment of inflammatory and immunocompetent cells
lectin complement pathway
lectin binding to pathogen surfaces=> opsonisation of pathogens
alternative complement pathway
pathogen surfaces=> killing of pathogens
B cell activation includes MHC-I or MHC-II
MHC-II
what T cell involved in B cell activation
CD4+ via CD40
where are T cells selected
Thymus
where do T cells mature and migrate into
The periphery
where do T cells circulate
through lymph nodes
IgG
main antibody in the blood, binds to bacteria and toxins. Only isotope that can pass through placenta
IgM
mainly distributed to the blood, produced first upon pathogen invasion by B cells, key role in initial immune system defence
IgA
In secretions of bowel fluid, nasal discharge and saliva to prevent bacterial invasion from a mucous membrane. Present in breast milk and products of the gastrointestinal tract of newborns
IgD
present on the surface of B cells and plays a part in the induction of antibody production at the prevention of respiratory tract infections
IgE
Originally related to parasites. By binding to mast cells it is involved in allegories
what enzyme is involved in complement pathway
proteases- catalysis proteolysis which breaks down proteins into smaller polypeptides
what does classical activation require
IgG and IgM
what is classical activation initiated by
C1 components
what does c1 cleave
C4 to form C4a and C4b. C4b then binds to pathogen and C2
what does the formation of c4b2a cleave
C3 which cleaves into C3a and C3b
what does C4b2a3b cleave
C5 which binds to surface of pathogen and then binds to C6, C7, C8 and monomers of C9 to form c5b6789n the membrane attack complex (MAC)
what is the alternative pathway initiated
C3 which is enzymatic cleaved by microbe to give C3b.
what does C3b bind to
Complement factor B form C3Bb complex. Exposes a site on Factor B that is a substrate for Complement factor D
Factor D cleaves Factor B to Ba and Bb
C3b and Factor Bb form C5 convertase (C3bBb) - Complement factor Properdin binds to C3bBb and stabilizes it on a pathogen’s surface
what does C3bBb forms make a complex with
C3b to form a C5 convertase activity
Pathway then continues in same way as classical pathway
what is the lectin pathway initiated by
mannan-binding protein, MASP-2 cleaves C4 and C4b-bound C2, generating C4b2a - lectin pathway C3 convertase, Continues as classical pathway
what do lysozymes break down
carbohydrate chains, and damages structural integrity of the bacterial outer membrane.
what do defensins do
disrupt membrane of the pathogen
where are cathelicidins stored
neutrophil granules as inactive precursors
