Question

1. How does a double positive T cell become a mature T cell? Include the selection process. 2. What is the effector function of CD8+T cells? How do they cooperate with CD4+ T cell effector functions? 3. What specifically drives the formation of each subset of Th effector cells? How do these Th effector cells respond once activated (i.e. what are their effector mechanisms?) 4. Describe in detail the signals in which an APC activates a T cell, and include induction of the third signal and all receptors and ligands. 5. How do the migration patterns of naïve and effector T cells differ? What drives the recruitment patterns of naïve and effector T cells to their target tissues?

Answer 1

1. The development of t cells ocuro in thymus. Double positive T cells are 004+ 1 CD48+. These thymocytes migrate deep into the thymic coolex, where they are presented with self antigens. The thy mic costical epithelial celle on MHC mole- cule expresses the self antigens to the cells. The double positive ab T cells more into colico medullary junction where they undergo positive and negative selecion and thus mature into th and Tc cells 2. The cost T cells are cytotoxic cells in they are killer cells. They are able to directly kill virus infected cells. They also kell cancer cells CD4 cells lead the fight against infections where as cos cells kill the cells The CD 4t helper I cells license the dendoitic cells to give a potent actrating signal to the native naive CD8+ T cells. The maluralion do Cp8+ Trelle is mediated by CD4 signalling

(Th1) 3). T helper i cells are required for host defence against intracellular viral and baderial pathogens. I helper (no) cells are required for host defence against large extracellular pathogens and are responsible for allergic respons Thelper type a (Th q) cells prolect against parasitic helminthic infectione. They cause asthma symptoms. 4) Signal 1 Siqnal 13, 2. Signal 2 102Tcel receptors CD4+) Trells) peptide MHC Tolerising APC Activated . APC cell activation T cell tolerance Two signals are required for the full aclia.com of T cells. Antigen specific is provided though TCR which interact with peptide MHC molecule on the membrance of APC. 2 Antigen non specific is provided by the interaction between co stimulatory mobil expressed on the membrane of APC & Talli