Most potent stimulator of naive T cell is?

There are 2 types of dendritic cells:Interdigitating dendritic cells and Follicular dendritic cells. Interdigitating dendritic cells - These are the most potent antigen presenting cells for T cells. These are present in the lymphoid tissues & non lymphoid organs. Immature dendritic cells present in the skin are called as Langerhans cells. They are non phagocytic & express high levels of MHC -II molecules & B7-1, B7-2. Follicular dendritic cells -Theses are present in germinal centers of lymphoid follicles. These can bind to antigen bound to antibody & present it to B cell. Ref: Robbins 8th Ed Pg 187.