Passage: MS is not considered a hereditary disease; however, a number of genetic variations have been shown to increase the risk. Some of these genes appear to have higher levels of expression in microglial cells than expected by chance. The probability of developing the disease is higher in relatives of an affected person, with a greater risk among those more closely related. In identical twins both are affected about 30% of the time, while around 5% for non-identical twins and 2.5% of siblings are affected with a lower percentage of half-siblings. If both parents are affected the risk in their children is 10 times that of the general population. MS is also more common in some ethnic groups than others.Specific genes that have been linked with MS include differences in the human leukocyte antigen (HLA) system—a group of genes on chromosome 6 that serves as the major histocompatibility complex (MHC). That differences in the HLA region are related to susceptibility has been known since the 1980s, and this same region has also been implicated in the development of other autoimmune diseases such as diabetes type I and systemic lupus erythematosus. The most consistent finding is the association between multiple sclerosis and alleles of the MHC defined as DR15 and DQ6. Other loci have shown a protective effect, such as HLA-C554 and HLA-DRB1*11. Overall, it has been estimated that HLA differences account for between 20% and 60% of the genetic predisposition. Modern genetic methods (genome-wide association studies) have revealed at least twelve other genes outside the HLA locus that modestly increase the probability of MS.

Question: What is the name of protection effect that ends with number four?
HLA-C554