TABLE 1.

Immunoabsorption of human platelet exosomes

Exosome preparation	CD81	GPVI	CXCL4	CXCL7	HMGB1
Platelet exosome precipitates	1842 ± 214	478 ± 24	9,953 ± 419	847 ± 22	422 ± 95
Immunopurified platelet exosomes	1399 ± 281*	555 ± 26	10,685 ± 543	996 ± 73	438 ± 101

Each value is the mean ± sem pg/ml (n = 4) for proteins extracted from exosomes released by 10⁸ platelets into 1 ml Tyrode’s buffer with 1 mM CaCl₂ in 30 min at 37°C and precipitated by ExoQuick-TC (upper row) or precipitated and immunochemically purified (lower row).

The mean quantity of exosomal CD81 in immunopurified samples is significantly less than in preceding precipitates by a paired Student's t test. For the other 4 proteins, none of the differences in quantity was significant after CD81 normalization to compare for the same amount of exosomes.

^*P = 0.011.