CTLA4 and rheumatoid arthritis: Through this approach it is possible to identify areas of homology between the RA-peptide and known human proteins We found that the RA-peptide shares homology with different self-antigens, such as: Protein-tyrosine kinase 2 beta (PYK2/FADK2), B cell scaffold protein with ankyrin repeats (BANK-1), Liprin-alpha 1 (LIPRIN-1), Cytotoxic T-lymphocyte protein 4 (CTLA-4) (Figure 3A).