The complexity of the immune system can be attributed to the
immense variety of immune cell types. Many immunologists have spent their time attempting
to familiarize themselves with several respective leukocyte subsets and ultimately
understand their specialized functions in the immune system. In 1973, the
discovery of the dendritic cell (DC) was a major breakthrough in the
classification of cells in immunology, for which scientist Ralph Steinman was
awarded the Nobel Prize in Physiology and Medicine in 2011. Before Steinman’s discovery,
immunology focused on the presence of antigens and lymphocytes. But the
discovery of the DC system shed light on the methods by which the immune
response was initiated and modulated. Langerhans cells (LCs) were first
visualized in the skin, however there was prolonged speculation as to what function
or purpose they served. It would later be known that LCs were a specific subset
of DCs. Steinmann identified a novel cell type in the spleen and other peripheral
lymphatic organs of mice (reference). The term dendritic cell was coined
after these cells distinct morphological features. At the time of DC discovery,
a link between activation of the innate immune system and the subsequent
priming of cells of the adaptive immune system was still missing. Several
experiments conducted on DCs derived from lymphoid tissues bridged this gap, establishing
them as potent stimulators of primary immune responses. Further studies of DCs
are hampered by their lack of specific DC markers, as well as their low frequency
in blood and tissues. Nevertheless,