JAK2 and myeloproliferative disorder: By contrast with normal cells, however, Ca2+ upregulates the levels of CALR expressed on the surface of erythroid cells from JAK2+ patients but not, as expected, in those from patients harboring CALR mutations with an impaired C-CALR domain which are unable to bind Ca2+ (Figure 5B), suggesting that under certain conditions anti-CD47/CALR therapies (see later) are likely to be effective in myeloproliferative neoplasms.