CTLA-4 Gene Cytotoxic T lymphocyte associated antigen-4 (CTLA-4) is considered as a negative regulator of T cell activation and its role in maintaining immune tolerance is well established. The present case-control study aimed to investigate the CTLA-4 +49 A/G, -1661 A/G, -318 C/T and -1722 T/C single nucleotide polymorphisms (SNPs) and predisposition to recurrent pregnancy loss (RPL) in Gaza Strip - Palestine.