Cell mediated immunity Flashcards
T-cells are selected in the thymus based on what two factors?
If they’re able to see MHC
If they’re able to see self
What is MHC? What are the 2 classes?
Major histocompatibility complex (glycoprotein) Class I or class II
Which cells express MHC class I on their surface?
All nucleated cells
Execptions: RBCs, platelets and nerve cells
Which cells express MHC class II on their surface?
Antigen presenting cells (APCs)
What are the functions of MHC class I and II?
Transport samples (peptides) of intracellular proteins to cell surface T cells constantly inspect surface of cells
Where are self proteins expressed? Which cells are they on?
Expressed on cell surface, within groove of MHC
All nucleated cells
Do circulating T-cells respond to self peptides on MHC-1?
No - only respond if abnormal peptide expressed on surface
What is meant by the MHC or genetic restriction of the immune response?
T-cells can only respond to antigens if they are presented in MHC molecule
What cell receptors bind to MHC?
T cell receptors
B cell receptors
(CD4 and CD8 can also bind)
Which cells are antigen presenting cells (APCs)?
Dendritic cells
Macrophages
B-cells
Basophils
Immunity can be naive or primed. Where do these different immune statuses start their response?
Naive - lymph nodes, at draining site of antigen exposure
Primed - local site of antigen exposure
What lymphoid tissues are involved with naive or primed immune response?
Naive - lymph nodes and spleen
Primed - MALT
How does naive or primed status affect immune response time?
Naive - slow >3 days
Prime - fast 1-2 days
What are the 2 routes of antigen entry into cells? Are these MHC class I or II restricted? (route of entry dictates what type of antigen processing and presentation)
Phagocytosis/endocytosis - MHC class II restricted Direct entry to cytosol - MHC class I restricted
What are the 2 types of antigen processing? What causes these?
Endogenous - caused by antigen entering cell via phagocytosis/endocytosis
Exogenous - caused by antigen directly entering into cytosol
Exogenous antigen processing involves the MHC class II pathway. Which cell recognises the antigens? What do they cause to be secreted?
CD4+ T helper lymphocytes (T cell receptor on this)
Cytokines
Endogenous antigen processing involves MHC class I pathway. Which cell recognises the antigens? What do they cause to be secreted?
CD8+ T cytotoxic lymphocytes
Cytokines
Antigen processing can be endogenous or exogenous. What type of pathogens does each respond to?
Endogenous - intracellular pathogens e.g. viruses
Exogenous - extracellular pathogens e.g. bacteria
Where do B cells mature? Where do T cells mature?
B - bone marrow or bursa of fabricus (birds)
T- thymus
What cell produces plasma cells?
B cells
What cell produces CD4+ and CD8+?
T cells
What are the 2 kinds of infections according to the immune system? What lymphocytes function in each?
Intracellular infection - cytotoxic T cells
Extracellular infection - B cells, secrete antibodies
Infections can be extracellular or intracellular. Do B cells or T cells work inside or outside of a cell?
B cells - outside a cell, produce antibodies to bind to pathogen
Cytotoxic T cells - inside a cell
Why can’t antibodies function during intracellular infections?
Antibodies cannot penetrate cell membrane
What causes clonal expansion?
Antigenic stimulation
Co-stimulation (activation of B or T cell stimulates proliferation)
What happens during clonal expansion? What cell does this happen to? What is this cell called after clonal expansion?
Lymphocyte cell enlarges
Stops migrating
mRNA and protein synthesis
Now called lymphoblasts- these divide
