Its presence in vesicles led to the suggestion, that, along with raft domains, annexin A7 plays a role in membrane organization and the vesiculation process. To examine this, we analysed the ability of red blood cells derived from the annexin A7 knock out mice (anxA7-/-) to form exovesicles. Because of better accessibility and larger available amounts that led to clear results, we included our data obtained with human blood. Independent of the presence of annexin A7 both types of exovesicles, micro- and nanovesicles, were released after Ca2+/ionophore treatment as determined by acetylcholine esterase activity and microscopic examination. Annexin A7 is present in both vesicle types where it is more enriched in nanovesicles (Fig. 2). The 51 kDa isoform is only detectable in nanovesicles. The quantity of both vesicle types did not differ between wild type and knock out red blood cell vesicles as determined by the AChE-values (A405 nanovesicles: ~0.18; A405 microvesicles: ~0.9; both, for wt and ko). It appears that annexin A7, although it has been described to fuse membranes, is not a key component in the process of the formation of red blood cell exovesicles. When we probed for the presence of sorcin in wild type and mutant vesicles we found that the sorcin levels were reduced in the mutant nanovesicles (Fig. 2).