Theme 4 - 4b (T cell activation pt 2 and T cell effector functions) Flashcards
what determines what specifc T helper cell a T cell will becomes
cytokines produced by APCs
what generally do T helper 1 cells do
mediate cell mediated immunity
what generally do T helper 2 cells do
mediate humoral immunity
what effect does signal 3 (polarising factors) have on the T cell
- induces TF activation
- causes T cells to produce different things eg T H 1 cells prod INTERFERON GAMMA and T H 2 produces IL4,5.13
how does CROSSREGULATION occur
- activation of ONE TF and thus development of TH1/TH2 cells will INHIBIT the development of th eother type of immune response
what is the master regulatory TF for TH1 cells?
T-Bet (activation of T-Bet inhibits activation of GATA-3)
what is the master regulatory TF for TH1 cells?
GATA-3 (activation of GATA-3 inhibits activation of T-Bet)
is the T H subset fixed
no, it can change as the immune response develops
do CD8+ T cells need MORE or less stimulation than TH cells to be activated
MORE (as they are cytotoxic)
- this is provided by CD4+ T helper cells (Th1 or Th17) that have recognised antigen on the APC
- the activation from CYTOKINES (IL-2) released from CD4+ T cells
- CD4+ T cells also ACTIVATE DCs via C40 TO CD40 ligand activation, this makes the DC BETTER at activating the CD8 T cell
what is the effect of CD40
- CD40L binds to CD40 on the APC, which stimulates it to make more co-stimulatory CD80/CD86 O ENHANCING activation of the CD8 T cell
in CD8+ T cell activation, what causes activation of CD4 T cells
the dendritic cell activates both CD8+ and CD4+
T cells must be activated by what
- by RELATED ANTIGENS presented by BOTH MHCI and MHCII on the SAME APC
what % of MHC class I molecules present peptides from EXOGENOUS antigens
25%, this is a process that isnt understood well
what is cross presentation
what is it important for
the presentation of EXOGENOUS antigens on MHC class I by unknown mechanism
- paramount for the activation of CD8+ T cells
what is cross presentation
what is it important for
the presentation of EXOGENOUS antigens on MHC class I by unknown mechanism
- paramount for the activation of CD8+ T cells
TH1 cells are involved in what type of mmune response
cell mediated immune responses (fighting INTRACELLULAR pathogens eg things taken up by macrophages or viruses in cells)
TH1 cells can interact with macrophages using WHAT LIGAND
where does this occur
CD40 LIGAND (CD40 L ) on T cell interacts with CD40 on APC induces macrohphage to be BETTER AT KILLING the microbe it has phagocytosed
- occurs in the PERIPHERAL tissue, where the infection actually is
TH1 cells can interact with macrophages using WHAT LIGAND
where does this occur
CD40 LIGAND (CD40 L ) on T cell interacts with CD40 on APC induces macrophage to be BETTER AT KILLING the microbe it has phagocytosed
- occurs in the PERIPHERAL tissue, where the infection actually is
what is the effect of Th1 cells at the periphery (that uses NEUTROPHILS)
- NEUTROPHILS are activated using TNF alpha (increased inflammation and microbial killing)
how do Th1 cells activate NK cells and CD8+ T cells
Th1 cells produce INTERFERON GAMMA which activates NK cells and CD8+ T cells which helps kill virally infected cells
what is the role of Th1 cells in the secondary lymphoid tissue
- produce INF-gamma which acts on B cells causing them to produce different IMMUNOGLOBULINS (IgG3 and IgG2a) which INC OPSONISATION and PHAGOCYTOSIS of microbes
- O allowing the macrophages to engluf the microbes more easily
briefly summaraise the 4 effector mechanisms of Th1 cells
1) in 2ndary lympohoid tissue, they release IFN-gamma which causes B cells to produce IgG3 and IgG2a which inc OPSONISATION and PHAGOCYTOSIS of microbes
2) in the PERIPHERY NEUTROPHILS are activated using TNF alpha (increased inflammation and microbial killing)
3) in the PERIPHERY CD40 LIGAND (CD40 L ) on T cell interacts with CD40 on APC induces macrophage to be BETTER AT KILLING the microbe it has phagocytosed
4) produce INTERFERON GAMMA which activates NK cells and CD8+ T cells which helps kill virally infected cells
what immune response do Th2 cells promote
humoral immune response
Th2 cells interact with B cells causing what
where does this occur
- in the secondary lymphoid tissue
- CD40L on Th2 binds to CD40 on B CELL
- and IL-4 production causes
- this causes the production of neutralising IgG antibodies (IgG4 human and IgG1 in mice) IMPORTANT for binding to SMALL soluble particles eg TOXINS so they can be NEUTRALISED
- also causes the production of IgE which is important in MAST CELL DEGRANULATION which can bind to PARASITES and HELMINTHS