The function of MARCHF8 (membrane associated ring-CH-type finger 8, ENSG00000165406) is as follows. E3 ubiquitin-protein ligase that plays several important roles in innate immunity and adaptive immunity (PubMed:34285233, PubMed:35019698, PubMed:35503863). Mediates ubiquitination of CD86 and MHC class II proteins, such as HLA-DR alpha and beta, and promotes their subsequent endocytosis and sorting to lysosomes via multivesicular bodies (PubMed:19117940, PubMed:19566897). Possesses a very broad antiviral activity by specifically inactivating different viral fusion proteins (PubMed:32934085). Targets and ubiquitinates cytoplasmic lysine residues of viral envelope glycoproteins with single transmembrane domains leading to their lysosomal degradation (PubMed:35019698). Therefore, shows broad-spectrum inhibition against many viruses including retroviruses, rhabdoviruses, arenaviruses, sarbecoviruses or influenzaviruses (PubMed:34285233, PubMed:35019698). Strongly blocks human immunodeficiency virus type 1 envelope glycoprotein incorporation into virions by down-regulating its cell surface expression. Also blocks ebola virus glycoprotein/GP incorporation via surface down-regulation (PubMed:32934085). Mediates 'Lys-63'-linked polyubiquitination of influenza M2 to target it to lysosome for degradation (PubMed:34285233). Mediates the regulation of constitutive ubiquitination and trafficking of the viral restriction factor BST2 within the endocytic pathway (PubMed:28320822). Plays a role in maintenance of immune tolerance to self by promoting the turnover and proteasomal degradation of PD-L1/CD274 via ubiquitination (PubMed:34183449). Catalyzes the 'Lys-63'-linked polyubiquitylation of cGAS thereby inhibiting its DNA binding ability and impairing its antiviral innate immunity (PubMed:35503863). Negatively regulates IL7- mediated T-cell homeostasis by mediating 'Lys-27'-linked polyubiquitination of IL7R, leading to its lysosomal degradation (PubMed:39311660). {ECO:0000269|PubMed:12582153, ECO:0000269|PubMed:14722266, ECO:0000269|PubMed:18389477, ECO:0000269|PubMed:19117940, ECO:0000269|PubMed:19566897, ECO:0000269|PubMed:28320822, ECO:0000269|PubMed:32934085, ECO:0000269|PubMed:34183449, ECO:0000269|PubMed:34285233, ECO:0000269|PubMed:35019698, ECO:0000269|PubMed:35503863, ECO:0000269|PubMed:39311660}. (Microbial infection) Mediates 'Lys-63'-linked polyubiquitination of hepatitis C virus/HCV protein NS2 which allows its binding to HGS, an ESCRT-0 complex component, and this interaction is essential for HCV envelopment. .