Innate Recognition Flashcards
What is innate antigen recognition?
It is the process by which the innate immune system identifies pathogens using pattern recognition receptors (PRRs) that detect pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs).
What are the two main methods of innate antigen recognition?
Direct recognition (via PRRs) and indirect recognition (opsonization by opsonins like antibodies and complement proteins).
What are pathogen-associated molecular patterns (PAMPs)?
Molecular structures conserved among pathogens, such as LPS (Gram-negative bacteria), flagellin, peptidoglycan, and viral ssRNA.
What are damage-associated molecular patterns (DAMPs)?
Host-derived molecules released from damaged cells, such as HMGB1, S100 proteins, ATP, and heat shock proteins.
What are the main classes of pattern recognition receptors (PRRs)?
- Toll-like receptors (TLRs)
- C-type lectin receptors (CLRs)
- NOD-like receptors (NLRs)
- RIG-I-like receptors (RLRs)
TLRs are membrane-bound PRRs that
detect extracellular and endosomal PAMPs.
NLRs detect intracellular bacterial infections and can
activate inflammasomes.
RLRs recognize viral RNA and trigger
antiviral responses.
Opsonization enhances phagocytosis by marking pathogens for
immune recognition.
DAMPs contribute to sterile inflammation, such as in
tissue injury and autoimmune diseases.
PRRs recognize highly specific antigens unique to each pathogen.
False – they recognize conserved molecular patterns.
TLRs occur as homodimers or heterodimers.
True
Opsonins include complement proteins like C3b and antibodies like IgG.
True
Inflammasomes are activated by NOD-like receptors.
True
PRRs recognize molecular structures called ______________ and ______________.
PAMPs, DAMPs
The receptor family that detects viral RNA in the cytoplasm is ______________.
RIG-I-like receptors - RLRs
Opsonins such as ______________ and ______________ facilitate phagocytosis.
IgG, C3b
The primary intracellular signaling pathway activated by TLRs is the ______________ pathway.
NF-κB signaling pathway
Which PRR is found on the plasma membrane and recognizes bacterial LPS?
a) TLR3
b) TLR4
c) RIG-I
d) NOD2
Answer: (b) TLR4
Which receptor type primarily detects fungal infections?
a) TLR5
b) CLR
c) RIG-I
d) NLRP3
Answer: (b) CLR
Which of the following is NOT a function of the complement system?
a) Opsonization
b) Direct pathogen lysis
c) Antibody production
d) Chemotaxis
Answer: (c) Antibody production
A patient with a bacterial infection shows increased C3b levels. How does this contribute to immune defense?
C3b functions as an opsonin, marking bacteria for enhanced phagocytosis by immune cells.
A viral infection triggers interferon production. Which PRRs are likely involved in this response?
RIG-I-like receptors (RLRs) detect viral RNA and activate antiviral pathways leading to interferon production.
A patient with sepsis has widespread inflammation due to bacterial endotoxins. Which PRR is likely overactivated?
TLR4, which detects bacterial lipopolysaccharides (LPS) and triggers strong inflammatory responses.
Pattern Recognition Receptors (PRRs):
Receptors that detect conserved microbial structures (PAMPs) and host damage signals (DAMPs).
Opsonization:
The process of coating pathogens with opsonins to enhance phagocytosis.
Toll-like Receptors (TLRs):
A class of PRRs that recognize bacterial and viral components to initiate immune signaling.
Inflammasome:
A multiprotein complex that activates inflammatory responses upon pathogen detection.
NF-κB:
A key transcription factor activated by PRRs to regulate immune responses.
