For example, PEG-PLA NPs [poly(ethylene glycol)-block-poly(D,L-lactide)] loaded with CTLA-4 siRNA efficiently restored the T-cell functions by downregulating CTLA-4 level and increasing the CD4+ and CD8+ T cell populations as well as inhibited tumor growth in mice with melanoma (Li S.-Y. Here, CD4 is linked to melanoma.