Levamisole was originally used as an anthelmintic to treat worm infestations in both humans and animals. Levamisole works as a nicotinic acetylcholine receptor agonist that causes continued stimulation of the parasitic worm muscles, leading to paralysis. In countries that still permit the use of levamisole, the recommended dose for anthelmintic therapy is a single dose, with a repeated dose 7 days later if needed for a severe hookworm infection.  Most current commercial preparations are intended for veterinary use as a dewormer in cattle, pigs, and sheep. However, levamisole has also recently gained prominence among aquarists as an effective treatment for Camallanus roundworm infestations in freshwater tropical fish . 
Perhaps more importantly, levamisole has been extremely productive in forward genetic screens. In the earliest studies tetramisole was used ( Brenner, 1974 ) and later this was replaced by the more active isomer, levamisole ( Lewis et al., 1980 ). These screens have provided a resource of mutants that have been used over the last two decades to assign function to genes expressed at the neuromuscular junction. Some of these are nACh receptor subunits, but others interestingly are not and serve to either regulate nicotinic receptors or muscle function (see Table 2 ).
In order to ensure an appropriate immune response , new vaccines and their development necessitate production of new generation adjuvants ( Nicholls et al ., 2010 ); ., use of cytokines viz., mucosal vaccine adjuvants such as IL-7 and IL-12 ( Stevceva et al ., 2006 ). Cytokines and chemokines viz., monocyte chemotactic proteins (MCPs), granulocyte-macrophage colony-stimulating factor (GM-CSF) and macrophage inflammatory proteins (MIPs) have been incorporated into vaccines most recently. This can be done in lieu of their (cytokines) potential to enhance recruitment of dendritic cells and monocytes from blood into the interstitial sites of vaccine delivery ( Klavinskis et al ., 2010 ). Killer cells, induced by cytokines like IL-2 and 15, can be used as vaccine against cancer ( Lee and Margolin, 2011 ; Thanendrarajan et al ., 2011 ). The important cytokines with their source, function along with their therapeutic application are listed in Table 4 .