1. There are three main classes of effector T cells that are specialized to figh
ID: 134984 • Letter: 1
Question
1. There are three main classes of effector T cells that are specialized to fight off different types of pathogens and produce different groups of cytokines. a. Name the three classes(or types of T cells b. List their functions C. Give a general example of an antigen for each class 2. What specific cytotoxins do cytotoxic T cells produce? 3. Describe the structure of the T-cell receptor. 4. Explain Self-MHC restriction of the T-cell receptor (TCR). 5. (a).Describe the mechanism for generation of diversity in the aß TCR (b). Why is this important? Based on your answer for the TCR, how is it important in B-cell/Ig diversity? 6. A large number of T cells are alloreactive. Explain how as many as one in 20 T cells can react to allografts. 7. What is thymic selection (education) and why is it important?Explanation / Answer
Ans,1
a. Three main classes of effector T cells are
TH1 , TH2 and TC cells
b. and C. Functions and example of antigen
TH1 - Th1 cells tend generate immune response against intracellular parasites such as bacteria and viruses.
TH2 - generate immune responses against extracellular parasites such as helminths.
TC cells- recognize antigens presented with MHC 1.
the targets can be virus-infected cells , cells infected with intracellular bacterial or protozoal parasites;
allografts such as transplanted kidney, heart, lungs, etc. and cancer cells.
2.
Cytotoxic T cells produce perforin and granzymes and store them in cytoplasmic granules.
3.
The T cell receptor is a heterodimer consisting of two transmembrane glycoprotein chains, the ? and ? chains (there are also a small proportion t cell receptors with ?? chains). the ? and ? chains each posses a constant (C) domain proximal to the cell membrane and a variable (V) domain distal from the membrane and the two chains are linked by disulfide bonds.
The short cytoplasmic tail of the TCR means it cannot directly signal when it binds to a peptide-MHC complex. Instead the TCR is associated on the cell membrane with a group of non polymorphic signalling molecules collectively called CD3 which transmit an intracellular signal when the TCR binds to a peptide-MHC complex.
4.
T-cell recptor does not recognize free antigens instead they recognize only antigen when it is presented by a self MHC molecule. this attribute is called as self-MHC restriction. for example TH cells recognize antigen with class II MHC molecules on APCs thus they are class II MHC restricted. similarly TC cells recognize antigen with class I MHC molecules on target cells thus antigen recognition by TC cells is class I MHC restricted.
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