Antigen-presenting cells.... When antigen-presenting cells (eg - macrophages, dendritics, etc) encounter antigens, do they all migrate to the lymph nodes? What causes them to do this? I know from sources I've read that dendrites do it, but do macrophages as well - or does the macrophage system rely on ones which are alread present in the nodes? Or do they just move around randomly in tissues, hoping to bump into a T / B cell? I cant seem to ifnd a detailed and clear site anywhere on the net! Thanks in advance.