Glycosylphosphatidylinositol anchored proteins (GPI-APs) are a type of natural conjugate found in the plasma membrane of eukaryotic cells. They are formed by attaching a glycolipid to the C-terminus of many proteins and play a crucial role in cell signaling and adhesion, with implications for health and diseases. On the surface of the protozoan parasite Toxoplasma gondii, both GPI-APs and GPIs without protein (free GPIs) are found in abundance. Serological assays have been developed to detect anti-GPI IgG and IgM antibodies to differentiate between toxoplasmosis patients and healthy individuals.