Life History of a T-cell part 2 Flashcards
(8 cards)
What are the four major classes of effector T-cells, and what is their main functions?
CD8 cytotoxic T cells - kill virus infected cells
CD4 T helper 1 cells - activate infected macrophages and provide help to B cells for antibody production
CD4 T helper 2 cells - provide help to B cells for antibody production, especially switching to IgE
CD4 T helper 17 cells - enhance neutrophil response
How are CD4 T cells specialised to deal with different classes of pathogens?
Th1 cells: Produce IFN-γ to activate macrophages (become highly microbicidal) and cytotoxic T cells, targeting intracellular pathogens like viruses and certain bacteria.
Th2 cells: Secrete IL-4, IL-5, and IL-13 to activate eosinophils and B cells, combating extracellular parasites like helminths.
Th17 cells: Release IL-17 and IL-22 to recruit neutrophils and enhance barrier defences, fighting fungi and extracellular bacteria.
What factors influence effector T-cell trafficking to different tissues?
Influenced by chemokine receptors, cytokines, integrins, and tissue-specific signals, which guide T cells to infection or inflammation sites for an effective immune response
Why do some effector T-cells remain in lymph nodes instead of migrating to tissues?
Specialized for functions like providing help to B cells, promoting antibody production, or regulating immune responses through interactions with other immune cells
How do TFH cells support isotype switching and somatic hypermutation in B-cells?
Provide essential signals through CD40L and cytokines like IL-21
These signals activate B cells in germinal centres,
- promoting isotype switching
- inducing somatic hypermutation to enhance antibody affinity for antigens
What is the significance of the enzyme activation-induced cytidine deaminase (AID) in antibody maturation?
AID catalyses somatic hypermutation of Ig genes leading to affinity maturation of antibodies in B cells
AID catalyses class switching of Ig constant regions leading to isotype switching of Abs
What are the hallmarks of a memory T-cell response compared to a primary immune response?
Faster - quicker B and T cell responses
Longer duration
Higher affinity antibodies
Why is the secondary immune response faster, longer-lasting, and more effective than the primary response?
The presence of memory B cells and memory T cells.
They are generated during the primary response and remain in the body for a long time
Upon re-exposure to the same pathogen:
- Large number of pathogen-specific cells respond immediately
- Pathogen-specific antibodies are already present
- Antibodies are isotype switched and have high affinity for pathogen
- Lower threshold of activation
- Effector T cells are present and can enter infected tissue immediately
- Close cooperation between innate and adaptive immunity from the start
