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Chapter

MICR 3230 Chapter Notes -Antigen, V(D)J Recombination, Memory T Cell


Department
Microbiology
Course Code
MICR 3230
Professor
Azad Kaushik

Page:
of 1
T Cell Maturation, Activation & Differentiation (Chapter 10) Summary
- progenitor T cells from bone marrow enter thymus and rearrange TCR genes
- thymocytes rearrange αβ TCR genes to become αβT cells.. small percentage
rearrange γδ to become γδ T cells
- DN (double negative) cells lack CD4 and CD8 (early thymocytes)
- During development, double negative thymocytes develop (expression of either
CD4 or CD8)
-Positive selection: eliminates T cells unable to recognize self MHC MHC
restriction
-Negative selection: eliminate thymocytes bearing high affinity receptors for self
MHC molecules (alone or self MHC plus self antigen) self tolerance
- T cell activation initiated by interaction of TCR-CD3 complex with a peptide-
MHC complex on an APC
- Activation requires accessory molecules including co-receptors CD4/CD8
- Intracellular signal transduction pathways activated by TCR engagement
- T cells expressing CD4 recognize MHC-II and function as TH cells
- T cells expressing CD8 recognize MHC-I and function as Tc cells
- Signal 1 TCR & accessory molecules
- Signal 2 TH co-stimulatory signal provided by APC
- Co-stimulatory signal induced by interaction between B7 on APC and CD28 on
TH cells
- Engagement of CTLA-4 (related to CD28) by B7 inhibits T cell activation
- Presence or absences of 2nd signal (co-stimulatory) determines whether activation
results in clonal expansion or clonal anergy (when only 1 signal is present)
-Naïve T cells are resting cells that have not encountered antigen
- Activation of naïve cells leads to generation of effective/memory T cells
-Memory T cells are easily activated and are responsible for secondary responses
-Effector T cells are short-live performing helper, cytotoxic or delayed type
hypersensitivity (DTH) functions
- T cell repertoire is shaped by apoptosis (-/+ feedback) in the thymus and
periphery