Lecture 10: T cell Mediated Immunity Pt. 2

activation requirements of naïve T cell

TCR, co-receptor binding and co-stimulatory molecule and IL-2

activation requirements of effector T cell

• requires TCR and co-receptor binding,

• does NOT need co-stimulatory molecule or IL-2

characteristics and roles of cytokines

• made by cells, affects the behavior of other cells

• changes gene expression of target cells

cytotoxins

made by cytotoxic T cells that help destory/kill target cells

overall function of CTL effector cell

kills target cells, suppress B cell activation

overall function of TH1 effector cell

inflammation, suppress B cell activation, activate macrophage

overall function of TFH effector cell

B cell response

overall function of TH2 effector cell

B cell response, suppress inflammation

overall function of TREG effector cell

suppress TH1 and TH2 activity

polarization

CTL lytic granules align to target cell

lytic granules

storage granules of CTLs and NK cells that contain cytotoxin

serial killer

CTL regenerates granules and kills serially as it engaged Ag on MHC

apoptosis

chromatin is cleaved by nucleases, chromatin condenses and the membrane is intact until late stages

two pathways of apoptosis

• 1st pathway: initiated by cytotoxic granules

  • proteases make pores in target cell membrane and deliver proteases into cytoplasm

  • proteases start apoptosis cascade

• 2nd pathway: initiated by binding Fas/Fas L

  • Fas L (on CTL) binds Fas (target)

  • signal to target cell starts apoptosis cascade

  • main pathway to dispose of unwanted lympocytes

angry macrophage

becomes more aggressive and efficent at killing intravesicular pathogens

what two signals does a helper T cell produce to make a macrophage angry

activated TH1 produces INFγ and binding of CD40 binds to CD40 L

2 main functions of TREG activity

TREG binds MHC on APC bound by autoreactive T cell, 2 main functions:

1. produces supressive cytokines (IL-10, TGF beta)

2. prevents production of new effector T cells and suppresses the function of existing effector T cells