Lecture 8 Flashcards
(31 cards)
What is an antigen?
any molecule or part of a molecule from disease causing organisms that is specifically recognized by the recognition proteins of lymphocytes
Define specificity
immune cells recognize and target specific antigens
Define memory
Faster, stronger response upon re-exposure to the same pathogen or antigen
Where are adaptive immune cells generated?
Primary lymphoid organs: thymus and bone marrow
Where are adaptive immune cells activated?
Secondary lymphoid organs: lymph nodes and spleen
What are the stages of adaptive immune response?
- Establishment of infection
- Induction of adaptive response (days)
- Adaptive immune response (weeks)
- Immunological memory (life-long)
What is a naive cell?
T and B cells that have undergone normal development, but have not yet been activated by antigens
Effector
Activated by antigen, differentiate from naive lymphocytes, can mediate removal of pathogens
Memory
B and T cells activated by antigen will differentiate into memory cells - sensitive to antigens, respond rapidly to re-exposure
What is the difference between an antibody molecule and T cell receptor structure?
antibody has two antigen-binding sites (variable region)
What genes encode the BCR and antibodies?
immunoglobulin (Ig)
What are epitopes?
Sites within antigens where antigen receptors bind
What happens after B cell binding?
proliferation and differentiation into plasma cells, secrete antibodies that have the same antigen specificity
Where are antibodies found?
in plasma and extracellular fluids
What are the three main ways that antibodies can participate in host defense?
Neutralization, opsonization, complement activation
Describe neutralization
bacterial toxins are recognized by cell receptors, antibodies tag and are ingested by macrophage
Describe opsonization
Bacteria in extracellular space are tagged, recognized by macrophage, ingested by macrophage
Describe complement activation
Bacteria in plasma are tagged, added to complement, undergo lysis and ingestion by macrophage
Describe the structure of a T-cell receptor (TCR)
Two chains: alpha and beta, with variable region and constant region. Not produced in a secreted form
What is the Major Histocompatibility Complex (MHC)?
group of cell surface proteins that play crucial role in antigen presentation and immune recognition, help distinguish between self and non-self antigens
What cells express MHCII? What does MHCII present?
dendritic cells, macrophages
presents extracellular antigens
What cells express MHCI?
What does MHCI present?
all nucleated cells: immune cells, epithelial cells, fibroblasts
present intracellular antigens
What is perforin?
forms pores in the target in the target membrane
What is granzyme
serine proteases, activate caspases to trigger apoptosis
