Anti-Ro/SSA can target Ro52 and Ro60 proteins. Most Anti-Ro/SSA activity occurs on the cell surface, wherein Ro proteins are expressed on the cell membrane and extracellular Anti-Ro/SSAs bind to Ro. There is some evidence that the IgG isotype of anti-Ro/SSA antibody can enter the cell.
* Anti-Ro autoantibodies are typically IgA, IgM, and IgG isotypes, though most is known about the five IgG subclasses. The antibody is inducible via immunization using Ro peptide.
The mechanism that induces Anti-Ro/SSA production in autoimmune disorders remains under study. Some proposed factors that may stimulate production are viral infection, treatment of cells with TNF-α, cellular apoptosis, and exposure to UV irradiation.
* Anti-Ro/SSA is produced in the cytoplasm of cells in the epidermal layer of the skin following UV irradiation. Ro antigens are simultaneously upregulated on the cell surface, resulting in the Anti-Ro/SSA antibody marking cells for destruction. Anti-Ro52 antibodies in particular have been tied to elevated photosensitivity.
Certain alleles of the human major histocompatibility complex (MHC II, called HLA II in humans) have been associated with the presence of Anti-Ro antibodies and the spread of the immune response. Anti-Ro/SSA associates with the HLA II alleles HLA-DR3 and HLA-DR2, as well as some HLA-DQ alleles. The T-cell response plays a role in the formation of Anti-Ro/SSA antibodies due to T-cell affinity for MHC class II.