usually not abundant at tumor sites, but increased densities of populations of dendritic cells have been associated with better clinical outcome, suggesting that these cells can participate in controlling cancer progression. lung cancers have been found to include four different subsets of dendritic cells: three classical dendritic cell subsets and one plasmacytoid dendritic cell subset. at least some of these dendritic cell subsets can activate cd4+ helper t cells and cd8+ cytotoxic t cells, which are immune cells that can also suppress tumor growth. in experimental models, dendritic cells have also been shown to contribute to the success of cancer immunotherapies, for example with the immune checkpoint blocker anti-pd-1. autoimmunity altered function of dendritic cells is also known to play a major or even key role in allergy and autoimmune diseases like lupus erythematosus and inflammatory bowel diseases (crohn's disease and ulcerative colitis). other animals the above applies to humans. in other organisms, the function of dendritic cells can differ slightly. however, the principal function of dendritic cells as known to date is always to act as an immune sentinel. they survey the body and collect information relevant to the immune system, they are then able to instruct and direct the adaptive arms to respond to challenges. in addition, an immediate precursor to myeloid and lymphoid dendritic cells of the spleen has been identified. this precursor, termed pre-dc, lacks mhc class ii surface expression, and is distinct from monocytes, which primarily give rise to dcs in non-lymphoid tissues. dendritic cells have also been found in turtles. dendritic cells have been found in rainbow trout (oncorhynchus mykiss) and zebrafish (danio rerio) but their role is still not fully understood media a dendritic cell