T Cell Activation Chapter 10

what initiates the adaptive response?

T cell and APC

how are APCs activated?

by pattern recognition receptors

what ensures that naive T cells recognize self?

positive and negative selection in the thymus

what are naive T cells?

ones that never met their antigen

what leaves the thymus and enters circulation as naive T cells?

CD8 and 4 T cells

why do naive T cells recircle?

if the T cell does not bind any of the MHC-peptide complexes it encounters and increases chances it will find its antigen

how do naive T cells leave the lymph node?

through efferent lymphatics through the thoracic duct back into circulation via the vena cava

what happens when the T cell does bind to an MHC-peptide complex?

it will stop migrating and it will initiate the program that leads to the production of cells that have both long-term and short term effects on infection.

costimulation

signal 2; generated by costimulatory receptors on the T cell and costimulatory ligands

who expresses costimulatory ligands?

professional APCs

how are APCs stimulated?

antigen binds to a PRR to express costimulatory ligand

what is the most common costimulatory molecule?

CD28 - note T cells express

what does CD28 bind to?

CD 80 and 86 (ligands)

function of cytokines

stimulate intracellular signals that enhance proliferation and survival

what cytokine plays a major role in T cell activation/proliferation?

IL-2

who presents MHC class 2?

DCS, activated macrophages and B cells

once T cells have received all 3 signals what is the next step?

become memory and effector helper or cytotoxic T cells

function of CD8 cytotoxic T cells

will circulate to sites of infection and kill infected cells

function of CD4 helper T cells

secrete cytokines that will orchestrate other cell types like macrophages + memory T cells (antibody production)

type 1 response

triggered by viral and many bacterial infections

type 2 responses

large parasites like worms and protozoa

type 1 polarization

TH1 and 17

type 2 polarization

TH2 and 9 to generate IgE

adjuvants

regulate the expression of costimulatory ligand to shape the response of T cell activation

TH1 helper type

IFN gamma IL-12 and 18

is CTLA-4 coinhibitory or a positive costimulator?

coinhibitory