Figure 6. PD-L1/2 deficiency results in enhanced CD4⁺ T cell responses to APCs in vitro.

Proliferative response of OVA peptide–specific CD4⁺ cells were measured when cultured with wild-type C57BL/6 (Control) or PD-L1/2^–/– APCs with or without lipid loading with acLDL in the presence of anti-CD3 or antigen stimuli. OVA pep, OVA peptide. (A) APCs were peritoneal macrophages (macrophage/T cell ratio, 2:1). (B) APCs were splenic DCs (DC/T cell ratio, 1:10). Incorporation of [3H]-thymidine was determined at 64 hours. (C and D) Cytokine secretion by the CD4⁺ cells cultured with DCs was measured in 48-hour supernatants. n = 3 per group. Data are mean ± SEM. *P < 0.05, ^†P < 0.01, ^‡P < 0.001 versus control; ^ζP < 0.05, ^#P < 0.01 versus control plus acLDL.