Considering a PD-1 pathway blockade as an immunological strategy to restore CTL function during chronic HIV infection (14, 17, 21), we investigated the effect of a PD-1 pathway blockade on both CXCR5− and CXCR5+CD8+ T cells in response to short-term TCR stimulation in vitro. The gene discussed is PDCD1; the disease is HIV infectious disease.