Lecture 9: T cells in infection Flashcards
Write some notes on the compliment cascade;
- Antigen-Antibody complexes can activate early components i.e C3.
C3 convertase enzymatically cleaves C3 which activates the compliment cascade i.e C3a, C3b
C3a drives Vasodilation, chemotaxis
C3b drives opsonisation it can also drive late stage component formation of membrane pores and subsequent lysis.
Why do we need more than antibodies when it comes to viruses?
Viruses grow inside cells and are therefore inaccessible to antibodies. i.e hepatitis infeciton
What is humoral immunity effective against? and some examples
- Product of B cells
- Involves antibodies
- Effect against antigens outside of cells
i.e Stops attachment of viruses and toxins. Enhance phagocytosis of extracellular bacteria.
What is cell mediated immunity effective against? and some examples
- Product of T cells
- No antibodies
- Effective against intracellular antigens (displayed on cell-surfaces)
i.e Virus infected cells, tumor cells, transplanted organs
What are the two types of T cells?
Cytotoxic (killer) T cells (CD3, and CD8)
Helper T cells (CD3 and CD8)
Describe t cell activation and the receptors involved;
Cytotoxic T cells (CD8, CD3, and TCR) binds Class 1 HLA (On antigen presenting cell) (Requires CD3 and CD8)
Helper T cells (CD4, CD3, and TCR) binds Class 2 HLA (On antigen presenting cell) (Requires CD3 and CD4)
Whats another name for HLA?
MHC (on surface of cells)
What are HLA?
Cell surface antigen presentation structures
Whats the properties of HLA class 1?
- Found on virtually all nucleated cells
- Co-dominant (mum and dad)
- Polymorphic
- Present peptides to CD8 T cells
Whats the properties of HLA class 2?
- Found on B cells and specialised APCs
- Co-dominant
- Polymorphic
- Present peptides to CD4 T cells
How do class 1 MHC end up presenting peptides?
Proteins naturally break down and since virus uses cell machinery these peptides are displayed.
What binds class 1 MHC from the APC?
TCr and CD8 binds HLA class 1
What does class 1 MHC activation lead to?
Following support by helper signals. The result in proliferation and differentiation of T cells forming cytotoxic T cells and memory cells.
Describe the process of class 2 MHC activation;
APC phagocytoses antigens and presents these on the surface using MHC class 2. These are presented to TCR on T helper cells. (Requires CD4 recognition of MHC class 2)
What does CD4 T helper cell activation lead to?
Following helper signals they proliferate and divide into CD4 cells that secrete cytokines and memory cells.
