Mutations in three of the proteins in the complement cascade have been identified in patients with atypical HUS . Several chemotherapeutic drugs have also been shown to cause damage to the epithelial layer by reducing the ability for the cells to produce prostacyclin, ultimately resulting in chemotherapy-associated HUS, or C-HUS.
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Sachs envisions " the ideal transgenic pig " as an animal with a variety of human genes working together against rejection : Genes to prevent human antibodies from binding to the pig organ, genes to inhibit the complement cascade and block endothelial-cell activation, genes that cause receptors to vital human growth factors and hormones to sprout on the pig cells.
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The graft is given a break from humoral rejection when the complement cascade is interrupted, circulating antibodies are removed, or their function is changed, or there is a change in the expression of surface antigens on the graft . This allows the xenograft to up-regulate and express protective genes, which aid in resistance to injury, such as heme oxygenase-1 ( an enzyme that catalyzes the degradation of heme ).
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In brief, the crucial role of C1q in the pathway is its importance as the first protein to start the complement cascade ( which ends in the destruction of the invading bacteria or virus ), and its ability to link the two important arms of the immune system the innate immune system : a broad defence system; and the adaptive immune system : the strong immune response capable of remembering previous infections, allowing fast response against recurrent infections, meaning that people with a normal immune system don't continually catch the same cold or same strain of flu repeatedly.
