CD8A and melanoma: As early as 2013, Weber et al. performed tetramer staining on leukocytes before and after treatment in 90 advanced melanoma patients receiving nivolumab in a Phase I study, and found that MART-126–35 antigen-specific CD8+ T cells slightly increased at 12 weeks post-treatment in patients with partial response (PR), complete response (CR), and stable disease (SD), but significantly decreased in patients with progressive disease (PD) [11].