T-Lymphocytes and Antigen Recognition Flashcards
What type of pathogen do T-Cells combat?
Intracellular, as antibodies can only attack extracellular pathogens
What does the T-cell receptor detect?
Antigen presented on MHC molecule of infected cell
What CD do all T-cells express?
CD3
What do CD4 receptors do?
Recognise antigens on MHC class II
What cells have CD4 receptors?
T helper cells
What do CD8 receptors do?
Recognise antigens on MHC class I molecules
What cells express CD8 receptors?
Cytotoxic T lymphocytes
What do CD3 molecules do, and what are they a part of?
Deliver signal to T-cell once antigen has been recognised.
Part of the T cell receptor (TCR)
What do CD4 cells do?
Secret cytokines to recruit effector cells and activate macrophages
What do CD8 cells do?
Are cytotoxic and kill target cells by secreting cytokines to induce apoptosis
What receptors do T-cells have when they arrive at the thymus (immature)
CD4-
CD8-
TCR-
When the TCR has been developed, what receptors are present on a T cell?
CD4+
CD8+
TCR+
How is a CD co-receptor removed?
By exposure of T-cell to MHC class I/II, determining the CD to be removed.
What percentage of T-cells survive selection?
5%
What does the Major Histocompatibility complex do?
Display sample of internal cell components for immune recognition.
Markers of self/health; continuously present
What are the 4 regions of MHC molecules?
Cytoplasmic
Transmembrane
Immunoglobulin like
Peptide binding
What size Peptides do each MHC class present?
MHC Class I: 8-10 amino acids
MHC Class II: >13 amino acids
What chains does an MHC Class I molecule have?
Alpha 1 Alpha 2
Beta 2 Alpha 3
(Beta 2 is microglobulin)
What chains does an MHC Class II molecule have?
Alpha 1 Beta 1
Alpha 2 Beta 2
What are the differences between MHC Classes I/II?
Class II has 2 cytoplasmic regions
Polypeptide chains are the same length in Class II
Which cells express MHC Class I?
All nucleated cells.
Levels may fluctuate during infection or by cytokines
Which cells express MHC Class II?
Professional antigen presenting cells
What are endogenous antigens?
Antigens that come from inside cells - use CD8 Class I restricted T-cells
What are Exogenous antigens?
Antigens from outside cells (e.g. phagocytotic and presented antigens) - Use CD4 Class II restricted T-cells