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Lecture

Lecture_8-_Summary.pdf

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Department
Immunology and Infection
Course
IMIN200
Professor
All Professors
Semester
Fall

Description
LECTURE #8 – T CELL DEVELOPMENT After studying lecture #8, you should be familiar with the following concepts. 1. The T Cell Receptor (TCR). T cells detect foreign antigen through the TCR. Each TCR is a heterodimer composed of an α and a β chain. Each chain contains a variable and a constant region. The variable region is responsible for antigen recognition. The TCR is permanently anchored in the plasma membrane and has no effector functions. Similar to the BCR, a TCR is generated through somatic recombination. V, J and C gene segments form the α chain and separate V, D, J and C gene segments form the β chain. Upon successful formation of an α chain at one locus recombination is shut off at the other α locus. This is referred to as allelic exclusion and it ensures that each T cell expresses a single α chain. Allelic exclusion also occurs at the β chain locus and during BCR rearrangement. 2. TCR – MHC interactions. The TCR interacts with antigenic peptides presented by MHC molecules (either class I or class II). The α chain and the β chain of the TCR interact with the peptide. Additional TCR residues interact with the MHC. The variable region of the TCR mediates TCR-MHC interactions. Stable formation of a TCR/MHC complex requires additional interactions of CD4 or CD8 on the T cell with the presenting MHC molecule. CD4 interacts with an invariant region of MHC II molecules and CD8 interacts with invariant regions of MHC I molecules. Thus, the class of cell presenting the antigen (i.e. MHC I or MHC II) determines the nature of the responding T cell (CD4 or CD8). 3. CD4 and CD8 T cells. CD4 T cells are also referred to as helper T cells. They interact with other immune cells such as B cells or macrophages and drive their activation. CD8 T cells are also known as
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