4. T-Cells I Flashcards
(17 cards)
What is the main difference between adaptive immunity and innate immunity?
Adaptive immunity has a slower response, highly specific targeting of individual pathogens, creates immunological memory, while innate immunity has an immediate response, targets groups of pathogens, and has no memory.
Innate immunity has limited diversity in pathogen recognition.
Why are T cells essential for the immune system?
They are crucial for combating infections and cancer.
Patients lacking T cells (SCID) historically died within 1 year.
What are the two main types of T cells?
- CD4+ T cells (helper T cells)
- CD8+ T cells (cytotoxic T cells)
CD4+ T cells help other immune cells function, while CD8+ T cells directly kill infected or cancerous cells.
What percentage of white blood cells are T cells?
Approximately 20% of white blood cells are T cells.
About 66% are CD4+ and 33% are CD8+.
What key functions do T cells perform?
- Direct killing of infected and cancer cells
- Helping B cells produce antibodies
- Producing cytokines to coordinate immune responses
- Activating other immune cells like macrophages
These functions are crucial for effective immune responses.
What are T Cell Receptors (TCRs) composed of?
TCRs are composed of alpha and beta chains with variable and constant regions.
Diversity is created through genetic recombination of V, D, J segments.
How many different T cell receptors can potentially exist?
Potential for 10^18 different T cell receptors.
Individuals typically have far fewer.
What do T cells require for antigen recognition?
T cells only recognize peptide antigens when presented in MHC molecules.
Unlike antibodies, T cells cannot recognize free-floating antigens.
What are the two types of Major Histocompatibility Complex (MHC)?
- MHC Class I: found on almost all nucleated cells, presents endogenous antigens
- MHC Class II: found only on professional antigen-presenting cells, presents exogenous antigens
Class I presents 8-10 amino acid peptides, while Class II presents 13-25 amino acid peptides.
What is the function of the Major Histocompatibility Complex (MHC)?
Acts as a scaffold to present peptide fragments to T cells.
Individual differences in MHC contribute to varied immune responses and determine transplant compatibility.
Where do T cells develop?
T cells develop in the thymus.
This is why they are called ‘T’ cells.
What is the first stage of T cell development?
Double-negative stage: Stem cells lacking CD4 and CD8 arrive in thymus.
This is followed by TCR rearrangement.
What occurs during positive selection in T cell development?
Only T cells that can recognize MHC survive; approximately 95% die.
This ensures that T cells can recognize foreign antigens.
What is the role of the Autoimmune regulator (AIRE) gene?
Enables thymic epithelial cells to express tissue-specific proteins from throughout the body.
This allows deletion of T cells that would react against self-tissues.
What happens when AIRE is knocked out in mice?
They develop multi-organ autoimmune disease.
This highlights the importance of AIRE in preventing autoimmunity.
What is the significance of the thymic selection process?
Ensures T cells can recognize foreign antigens while avoiding self-reactivity.
Each mature T cell can only recognize one specific peptide in the context of MHC.
What can defects in T cell development or function lead to?
Severe immunodeficiency or autoimmune disease.
This underscores the importance of proper T cell functioning in immunity.
