Studies of the concentration of iron and molybdenum in the immune-privileged organs of rats without a pathology and after simulating posthemorrhagic anemia, which received intramuscular injections of Keplerate-type nanocluster porous spherical polyoxometalate (POM) {Mo72Fe30}, are conducted. The blood–testis barrier is the most resistant to the penetration of the components of POM, the blood–brain and blood–ocular barriers possess a lower resistance (accumulation of iron after 30 injections of POM), and the blood–thymus barrier is the least resistant. The borrowing of iron from immune-privileged organs such as the brain, eyeballs, and thymus occurs in the early stages (1 to 7 days) of posthemorrhagic anemia. Posthemorrhagic anemia decreases the resistance of the blood–brain barrier and is accompanied by the excessive accumulation of iron after seven injections of POM.