GPI anchor–negative cells do not present antigenic peptides of GPI-anchored proteins on MHC class II molecules.

CD4⁺ T cells isolated from a TCR-transgenic mouse (OTII) were mixed with EL4 cells transfected with various forms of OVA and treated with mitomycin C. Proliferation was assessed on day 4. TM-OVA indicates EL4 cells transfected with the transmembrane form of OVA; GPI-OVA, EL4 cells transfected with GPI-anchored OVA; native OVA, EL4 cells transfected with native OVA; vector, vector-transfected EL4 cells; ▨, EL4 cells defective in GPI anchor biosynthesis; ▪, EL4 cells with normal GPI anchor biosynthesis; and ■, GPI⁻ EL4 cells pulsed with OVA peptide. Data (mean + SD of duplicate samples) were from a representative of 7 experiments, all with similar results.