B7.2 is dispensable, and ICAM-1 is required for increased immunogenicity in mature exosomes. (A,B) ³H-thymidine incorporation by Marilyn T cells cultured with HY peptide and mature BMDCs either WT or deficient for B7.1 and B7.2 (A) or ICAM-1 (B). One representative experiment out of 5 (A) or 2 (B). (C) Western blot analysis of exosomes purified from mature WT, B7.1,2-deficient (B7^–/–), or ICAM-1–deficient (Icam^–/–) BMDCs. (D-G) ³H-thymidine incorporation by Marilyn T cells cultured with WT (D,F), or B7^–/– (E), or Icam-1^–/– (G) spleen DCs, and HY-bearing mature exosomes from WT, B7^–/– (D,E), or Icam-1^–/– (F,G) BMDCs. One representative experiment out of 2. Panels D and E on one side, and F and G on the other, were from the same experiment.