T Cells Flashcards
Outline how endogenous antigens are made
Endogenous antigens made be derived from intracellular viral or cancerous proteins. Viruses infect cell and commandeer there machinery to make viral proteins (for viral replication). Cancerous cells have abnormal changes in DNA code, which cause these cells to build abnormal proteins.
Outline MHC 1 antigen processing
Antigenic proteins (viral/cancerous) are degraded in cytoplasm
Peptide loading of MHC 1 takes place in the endoplasmic reticulum
Outline MMHC 2 antigen processing
Antigen intake via phagocytosis into a phagolysosome.
Antigenic proteins are degraded in acidic phagolysosome
Peptide loading of MHC 2 takes place in phagolysosome
What are T cells
Lymphocytes that arise in the bone marrow (diving stem cells) and fully develop in thymus.
T cells express T cell receptor (TCR) with co receptors (either CD4 or CD8)
Recognise MHC/peptide complexes
Expand on the rearranging of T cell receptor DNA
Occurring in the thymus, the DNA regions that code for the T cell receptors are rearranged. This results in various T cells having various receptors, leading to diversity of T cell receipting capability throughout the body.
T cell clonal replication then multiplies the number of specific T cells within the body.
Outline antigen triggered T cell clonal replication
If a T cells TCR binds antigen and associated MHC complex with enough affinity, then T cell undergoes clonal expansion while retaining specific initial TCR sequence.
Outline the production of T cells
T cells begin as products of stem cell replication in bone marrow. Immature T cells then migrate to the thymus where they mature. T cell development and TCR gene rearrangement occurs in thymus. Screening process screens out self attacking T cells. After T cell education in thymus, mature T cells move onto lymphoid organs, blood, tissue.
Outline Thymic gene rearrangement
Immature T cells (thymocytes) rearrange the variable parts of their TCR genes in thymus.
Th rearrangement process is essentially random.
This ensures that individual T cells are unique in terms of their TCR. Creates diversity in T cell repertoire.
What are naive T cells
Mature T cells that have not seen an antigen
What is the main function of CD4 and CD8 co receptors
Work alongside T cell receptor, helping interact with correct MHC protein on antigen presenting cells
Outline the preferential binding of CD4 and CD8
CD4 preferentially binds with MHC 2
CD8 preferentially binds with MHC 1
What are effector T cells
Activated T cells
Outline CD4 T helper cell
Recognises MHC 2/ extracellular peptides
Helps B cell make antibodies
Helps CD8 T cell become cytotoxic (release of cytokine growth factors that activate CD8)
Outline CD8 T cell
Recognise MHC1/ intracellular peptide (viral/cancerous)
Develop into cytotoxic T lymphocytes/Cytotoxic T cell
Outline the conjoint activation of CD4 and CD8, especially in a viral sense
CD8 T cells activated by MCH1, however really need cytokines (produced by CD4 - also activated) to activate. Particularly for viral responses, multiple cells need to be activated. CD4 helper cell activates CD8 T cell
