Molecular Biology Of The Cell 6th Edition by Bruce Alberts, Alexander Johnson, Julian Lewis, David Morgan, Martin Raff, Keith Roberts, Peter Walter

تمرين 16

Which statements are true? explain why or why not.
-Before exposure to a foreign antigen, T cells with receptors specific for the antigen are a tiny fraction of the T cells-on the order of 1 in 10? or 1 in 10? T cells. After expo- sure to the antigen, only a small number of dendritic cells typically display the antigen on their surface. How long does it take for such antigen-presenting dendritic cells to interact with the antigen-specific T cells, which is the key first step in T cell activation and clonal expansion? The dynamics of the search process were examined by labeling dendritic cells red and T cells green, so that contacts in an intact lymph node could be scored visually using two-pho- ton fluorescence microscopy (Figure Q24-3A). The fre- quency of contacts between dendritic cells and T cells from such experiments is given in Figure 24-3 b. Assuming that 100 dendritic cells present the specific antigen, how long would it take them to scan 10? T cells? How long for 10? T cells?