Acquired Flashcards
(39 cards)
Cells of lymphoid cycstem
T (CD4 and CD8)
B
NK
What is the process of formaiton of T cells
Produced in bone marrow
Migrate to Thymus where they mature
How do T cells mature?
Development of T cell receptor
- Cell surface bound protein structure that binds to antigen
TCR binding results in T cell activation and proliferation
TCR testing in thymus - if autoactive - rearrange TCR or undergo apoptosis (clonal deletion)
What can activate a T cell
MHC antigens
Antigen presenting cells
Antigen processing
What are MHC class I cells? What do they present to?
Expressed on all cells
Present to CD8+ T cells
What are MHC class II cells? What do they present to?
Expressed on selected cells such as APCs
Present to CD4+ T cells
What are MHC antigens called in uhmans?
HLA human leukocyte antigens
What do MHC class I cells do
Found on all cells and continuously present broken down peptides .
Constantly proving to the immune system that it is a healthy cell
If a cell becomes infected or a tumour it will start presenting foreign peptides on MHC I molecules stimulating CD8 cells to destroy it
What is cross presentation
Presentation of exogenous material on MHC I receptor
Occurs when APC takes up a cell that contains foreign antigen
Material broken down and presented on MHC II receptor but some debris peptide enters cytoplasm and this is presented on MHC I
CD8 activated and responds
MEchanism of graft rejection
What are MHC class II molecules?
Presented by specialised APCs which take up exogenous pathogens, phagocytose them and present peptide products.
MHC II molecule bind with peptide and travel to cells urface
Antigen/MHC presented to T lymphocytes
How does MHC maximise immunity?
Polygenic - several different MHC class I and II genes
Polymorphic - multiple variants of each gene increasing potential number of peptide combinations that can be presented
What is alloreactivity?
Recognition of non-self tissue from the same species as foreign
2 methods:
1. Recognition of foreign HLA molecule
2. Recognition of presented tissue derived peptide as pathogenic
What are APCs
Dendritic cells
- Myeloid - produce IL12
-Plasmycytoid produce IFN 1
MAcrophages
B cells
CD8 vs CD4 T cells
CD8 recognise MHS class I molecules presented antigens
CD4 recognise MHC class II presented antigens
What do CD8 T cell granules contain
Membrane disrupting proteins - perforin, granulysin
Serine proteases - granzymes
Lysosomal eznumes
Stored effector molecules - FasL - binds to Fas expressing cells to induce apoptosis
What in the role of CD4 cells?
Secreting cytokines to upregulate responses
What do Th1 cells secrete?
IFN - gamma
- Activates macrophages, enhancing antigen presentation to T cells, increasing phagocytosis
IL-12
Drive DC activation and presenation
Express CD40 stimulatory molecule - amplifies response
What do Th2 cells secrete
IL4, IL5 IL6
IL13
Stimulate antibody production and mucous secretion
What do Th17 cells secrete
IL17
What CD4 cells are involved in allergy and parasitic infections
Th2
What is IL 17
Potent neutrophil chemoattractant
What is a cytokine
Cell derived soluble mediator
What are anti inflammatory cytokines?
IL10
TGF beta
Downregulate CD4 cell responses
IL4 (antagonises IFN-ga)
What are functions of cytokines?
Cytotoxic - TNFa
Growth factors - IL4 for B cells
Synergistic to enhance response - IL1 enhances IL8
Clonally expanding cells - IL2 promotes expansion of activated CD4
Cell attractants/chemokines IL8 attracts neutrophils
