Question

1) CD8+ Tc cells can be activated by any pAPC.  a. True b. False

2. licensing of dendritic cells requires interactions with Th cells. a. True b. False

3. the message coding for the TCR can be alternatively spliced to create two different forms of the receptor. a. True b. False

4. by the time a DN thermocyte reaches the thymus it is commited in fate to become either a Th1 cell or a Th2 cell. a. True b. False

5. the details for how a T cell becomes a single positive cell are well understood. a. True b. False

Answer 1

1) CD8+ Tc cells can be activated by any pAPC.

Ans b. False - pAPC expresses high levels of MHC class II molecules to present extracellular antigens to CD4+ Tc cells and thus activating them.

2) licensing of dendritic cells requires interactions with Th cells.

Ans b. False - Dendritic cells have their own machinery to present the antigen on its MHC II molecules and do not require interactions with Th cells. These cells engulf the large pathogen or foreign particles and by the process of phagocytosis degrade the pathogen leaving behind the smaller foreign molecules called antigen to be presented on its surface. Inorder to activate other T cells and B cells there is an interaction of Th cells with Antigen presenting dendritic cells.

3) the message coding for the TCR can be alternatively spliced to create two different forms of the receptor.

Ans b. False - Two different forms of the TCR are the resulatant of VDJ gene rearrangement. There are basically two types of receptors - alpha beta receptor and gamma delta receptors. Variability in each of these receptors are the resultant of splicing mechanism.

4) by the time a DN thermocyte reaches the thymus it is commited in fate to become either a Th1 cell or a Th2 cell. a. True b. False

Ans b. False - DN thymocyte undergo maturation and two kinds of selection processes (negatice selection and positive selection) to generate naive T cells inside the thymus. Further these naive CD4+ precursor cells differentiate to TH1 and Th2 through the process governed by the interleukins IL12 and IL4, or by signalling through the Notch receptor.