In humans CD53 deficiency has been associated with recurrent infectious diseases caused by bacteria, fungi and viruses [46], and polymorphisms in the gene have been associated with regulation of TNF-α levels [47]; up-regulation of TNF-α has been observed in the abomasal lymph node of sheep challenged with T. circumcincta 5 days after infection [48], and abomasal mucosa of resistant DRB1*1101 carrier lambs at 3 days post infection [49]. Here, TNF is linked to infectious disease.