any final confusions Flashcards
dsDNA class 1 viral replication
replication in host nucleus, using DNA-dependent RNA polymerase to make viral mRNA
no other enzymes required
adenovirus, herpesvirus
ssDNA class 2 viral replication
replication in nucleus
host DNA polymerase converts ssDNA —> dsDNA
host RNA polymerase makes mRNA
no viral polymerase needed, only host enzymes
parvovirus
dsRNA class 3
host cells cannot read dsRNA directly
replication:
1. virus brings own RNA dependent RNA polymerase (RdRp)
2. RdRp copies negative strand into positive sense mRNA so can be translated now
virus must bring RdRp inside capsid when infecting
rotavirus
+ ssRNA class IV viral replication
postive sense RNA is same as mRNA so read directly
viral genome acts as mRNA so translated into viral proteins, making viral RdRp first to replicate the RNA genome from that
poliovirus and covid
- ssRNA class V viral replication
negative sense is complementary to mRNA so cannot be read directly
virus brings own RdRp into host cell
RdRp copies -RNA into + mRNA for translation
influenza
+ssRNA class VI viral replication
viral reverse transcriptase copies RNA into DNA
DNA integrates into host genome via integrate enzyme
host RNA polymerase makes mRNA and new genomes
HIV
dsDNA gapped class VII viral replication
genome is partially double stranded DNA
host repairs gaps to make full dsDNA
host RNA polymerase transcribes
teichoic acid
gram positive bacteria
- involved in adhesion/colonisation
- inflammatory response
- activation of complement and release of cytokines
detected by TLR2
highly antigenic - PAMP
LPS
gram negative bacteria
Lipid A - endotoxin, causes sepsis, high fever
O-antigen - highly antigenic, helps evade immune detection
immune activation, causes inflammation cytokines production like TNF-A IL-6
protect against antibiotics and host defences
detected by TLR4
IgM
lowest affinity as present on naive B cells, before affinity maturation (somatic hypermutation)
pentamer
activates complement system effectively
opsonisation
IgD
not fully understood
with IgM on naive B cells
monomer
IgG
most adundant antibody
monomer
can cross placenta to provide passive immune city to fetus
complement activation, opsonisation and ADCC
neutralisation of pathogens
FcyR on macrophages
IgE
allergic responses, defence against parasites
monomer
key role in mast cell and basophil activation to release histamines
opsonisation
FceR on mast cells
IgA
mucosal immunity
monomer in body and dimer in secretions
bad at opsonisation
least inflammatory causing
neutralisation effects - protect mucosal surfaces from infection
FcaR - macrophages
somatic hypermutation
this is affinity maturation
occurs in germinal centres of LN
somatic recombination
this is isotype switching via VDJ recombinase
ADCC
antibodies bind to pathogens/ infected cells
the FC region binds to receptors on immune effect cells like NK, macrophages etc
this causes immune cell to activate and release toxic molecules that can induce cell death to target cell or phagocytosis
NK cells
innate
killing infected cells
recognise stressed or infected cells via an imbalance in activating and inhibitory receptors - like down regulation of MHC 1
kill target cells via perforin and granzymes to cause apoptosis
also use ADCC
secrete IFN-Y TNF-a
activated by type 1 interferons
neutrophils
innate cell
recognise pathogens via PRRs
kill pathogens through phagocytosis, ROS, lysomes, defensives
use NETosis to trap and kill pathogens outside cell
secrete - IL-1, TNF-A
activated by - IL-1 TFN-A IL-8
mast cells
innate , involved in allergy response
sweep and weep
release histamine, cytokines to cause inflammation
activated by IgE antibodies binding, cross linking activates mast cells to degranulate
secrete - histamine, TNF-A IL-4
activated by - IGE, C3A C5A IL-1
basophils
innate cells, allergies response
similar to mast cells, but less abundant and understood
IgE bind to degranulate
eosinophils
innate
involved in combating parasites and allergens
release toxic protein to damage parasites and cytokines
secrete - IL-4 IL-5 IL-13, MBP
activated - IL-5 IGE
macrophages
innate cells
phagocytosis and APC
recognise via PRRS
present antigens MHC2 to T cells
activated - IFN-Y IL-4 TNF-A C5A
SECRETE - IFN-Y TNF-A IL-1 IL-6 IL-10
CTLs
adaptive immune cells
CD8+ to kill infected cells and cause apoptosis
recognise via MHC 1
release perforin and granzymes to cause death
or FAS/FASL
ACTIVATED - IL-2 IL-12 IFN-Y
SECRETE - IFN-Y TNF-A
Th cells
adaptive cells
coordinating immune response and activating other cells
Th1 activate macrophages and CTLs to fight intracellular pathogens
Th2 help B cells product IgE to play role in allergy response and helminth infections
Th17 produce IL-17 to contribute to inflammation in autoimmune and fungal infections
Tfh help B cells product antibodies
Treg cells
adaptive cells
maintaining immune tolerance and prevent autoimmune diseases
suppress the immune system using IL-10 and TGF-B
