T Cell Development Flashcards
Location of T cell development
Thymus, then migrate to secondary lymphoid tissue
T cells only recognize _____
peptide antigens
T cell receptor immunoglobulin characteristics
membrane anchored
2 chains, each with a single constant and single variable domain
The two variables form the antigen-binding region
Gamma/Delta T cell characteristics that differ from T cells
Not part of acquired immune response Recognize lipid rather than peptide antigens Mature extrathymically CD4 and CD8 negative found in mucosal epithelial of the gut
CD3
signal transduction unit, targets the nucleus when T cell binds its cognate determinant
all 6 subunits involved in signaling
ITAMS
on CD3, critical for initiation of signaling cascade.
CD28
on T cells, binds to co-stimlator B7 that is expressed on antigen presenting cells when they encounter a pathogen
FAS ligand
on T cells, binds 3 FAS protein and leads to apoptosis
Adhesion molecules
Facilitate the interactions between T cells and antigen presenting cells, vascular endothelial cells, and potential target cells. All cell-to-cell interactions involving immune cells are initiated by adhesion molecules.
CTLA-4
expressed on active T cells, has similar mechanism as CD28 but better binding affinity. serves as a “brake” and inhibits T cell activation and proliferation
PD-1
binds PDL-1/2 and prevents T cell activation and proliferation, critical for preventing activation of self recognizing T cells
cell types of the thymic cortex
macrophages
thymocytes
cortical epithelial cells
cell types of the thyme medulla
macrophages
dendritic cells
hassalls corpuscles
thymocytes
tingible macrophages
macrophages of the cortex that phagocytose thymocytes
negative selection occurs in _____
the bulk of it in the medulla but some also in the corticomedullary junction
pTalpha chain
an invariant chain that serves as a surrogate alpha chain so that a pre-T cell receptor complex can form. critical because beta chain develops first and is not stable when unbound
positive selection of thymocytes
occurs in the cortex via cortical epithelial cells which display MHC class I and II molecules. T cells that are able to bind tightly are positively selected for while others undergo apoptosis/are engulfed by tangible macrophages
negative selection
occurs mostly in the medulla, any cells that binds too tightly to MHC class I or MHC class II undergoes apoptosis
AIRE
autoimmune regulator, transcription factor that drives expression of proteins not native to thyme function so that development of the T cells is not detrimental to the function of the thymus, also helps eliminate self-reactive T cells from repertoire
Hassal’s corpuscles
produce TSLP cytokine and drives some self reactive CD4 T cells to differentiate into Treg cells instead of undergoing apoptosis
Tregs
EFFECTOR CD4 T cells that help prevent self-reactive T cells from having detrimental affects in the peripheral tissues
T/F Self reactive T cells are more likely to be positively selected for in the cortex
true, this is why negative selection is so important
