Immunology: Initiation of Acquired Immune Responses - T Cells

Question 1

what do T cells recognise

Answer 1

peptide antigens expressed on MHC molecules

Question 2

MHC-I molecules are expressed on what type of cell and present to what type of cells

Answer 2

• all nucleated cells

- CD8+ T cells

Question 3

MHC-II molecules are expressed on what type of cell and present to what type of cells

Answer 3

• only antigen-presenting cells

- CD4+ T cells

Question 4

what cells are antigen-presenting

Answer 4

dendritic, macrophages, B cells

Question 5

how do dendritic cells present antigens to T cells

Answer 5

• after phagocytosis in inflamed tissues dendritic cells phagocytose debris via PAMPs and PRRs
• TNF alpha stimulates dendritic cells increasing their expression of co-stimulatory molecules
• antigen proteins are displayed on MHC-II and the maturing cell drains into lymph nodes
• here it presents to T cells

Question 6

what 2 signal do T cells need to activate

Answer 6

• peptide from MHC

- second signal from dendritic cell

Question 7

how are T cells differentiated

Answer 7

• a niave CD4+ cell recieves the two signals required allowing for proliferation
• the now Th0 cell differentiates into effector T cells - Th1, Th2, Tfh or Treg

Question 8

what is the function of Th0 cells

Answer 8

secrete IL-2 and differentiate into effector T cells

Question 9

where does T cell differentiation take place

Answer 9

lymph nodes

Question 10

what is the function of Th1 cells

Answer 10

• go to sites of inflammation via transendothelial inflammation
• macrophages reactivate the T cells via MHC-II presented antigens
• Th1 cell secrete pro-inflammatory cytokines andhacing ROS phagocytosis by macrophages

Question 11

what is the function of Tfh cells

Answer 11

• B cells present antigen via MHC-II
• T cell moves to B zone and are re-stimulated by B cells
• it then stimulates B cells to clonally proliferate and differentiate into long lived plasma cells/memory B cells

Question 12

what is the function of CD8+ T cells

Answer 12

proliferate and differentiate into cytotoxic T lymphocytes where they enter inflammatory sites and kill virally infected cells

Question 13

how to cytotoxic T cells kill host cells

Answer 13

• cell recognises and binds to virally infected cell (via MHC)
• T cell programmes for cell death and DNA fragmentation
• cell migrates to new target and apoptosis occurs

Question 14

how do inflammatory sites return to normal after inflammation

Answer 14

• anti-inflammatory cytokines (IL-10) repairs tissue damage

- T and B cells die leaving memory T and B cells