During this process, the parasite releases the toxic and soluble molecule heme. The heme moiety consists of a porphyrin ring called Fe(II)-protoporphyrin IX (FP). To avoid destruction by this molecule, the parasite biocrystallizes heme to form hemozoin, a nontoxic molecule. Hemozoin collects in the digestive vacuole as insoluble crystals.Chloroquine enters the red blood cell by simple diffusion, inhibiting the parasite cell and digestive vacuole. Chloroquine then becomes protonated (to CQ2+), as the digestive vacuole is known to be acidic (pH 4.7); chloroquine then cannot leave by diffusion. Chloroquine caps hemozoin molecules to prevent further biocrystallization of heme, thus leading to heme buildup. Chloroquine binds to heme (or FP) to form the FP-chloroquine complex; this complex is highly toxic to the cell and disrupts membrane function. Action of the toxic FP-chloroquine and FP results in cell lysis and ultimately parasite cell autodigestion. Parasites that do not form hemozoin are therefore resistant to chloroquine. Resistance in malaria
Since the first documentation of P. falciparum chloroquine resistance in the 1950s, resistant strains have appeared throughout East and West Africa, Southeast Asia, and South America. The effectiveness of chloroquine against P. falciparum has declined as resistant strains of the parasite evolved. Resistant parasites are able to rapidly remove chloroquine from the digestive vacuole using a transmembrane pump. Chloroquine-resistant parasites pump chloroquine out at 40 times the rate of chloroquine-sensitive parasites; the pump is coded by the P. falciparum chloroquine resistance transporter (PfCRT) gene.
Anaphylaxis

Prevention
To prevent allergic transfusion reaction it is possible to use patients own blood for transfusion, this is referred to as autologous blood transfusion. Patients own blood is collected and washed to produce concentrated red blood cells (this blood product is also called packed red blood cells). There are multiple ways to wash red blood cells. The two main methods that are used to wash the cells are centrifugation, or filtration methods like the Hemoclear microfilter. The last option is reinfusion without washing. This is the least preferred method because of the chance of complications.There is no evidence that antihistamine premedication prevents allergic transfusion reactions, although these drugs can mitigate symptoms once they occur. Treatment
Treatment of an allergic transfusion reaction is to immediately stop the transfusion. If the only symptoms are mild (i.e., hives and itching), the patient may be treated with an antihistamine and if the symptoms completely disappear and the patient feels well, the transfusion may be restarted. A mild transfusion reaction during infusion usually does not progress to a more severe anaphylactic reaction after infusion of additional product from the same unit. If the symptoms are more than mild, the transfusion should not be restarted. == References ==