There is a moderate scientific literature on the immunological effects of extracts from plants of the genus Aloe. Unfortunately, it is difficult to assess the significance of many of these studies because of two problems. First, most studies have been undertaken using many different, poorly characterized, complex aloe extracts. Second, studies have been performed using several different Aloe species, making comparisons impossible. Although anecdotal reports describe a wide variety of both immunostimulating and immunosuppressive effects, controlled scientific studies have substantiated very few of these. Most studies that have been performed have focused on the clear mesophyll gel of the Aloe vera leaf and on its major storage carbohydrate, acetylated mannan (aceman-nan). Recently a unique pectin has been isolated from aloe mesophyll cell walls and appears to have unique and important properties. Some consistent properties have, however, been noted. Thus aloe gel extracts and partially purified acemannan preparations have mild anti-inflammatory activity and multiple possible pathways for this activity have been investigated. Aloe extracts also have some limited macrophage activating properties. These include the release of nitric oxide and the secretion of multiple cytokines. This macrophage activation may account for the effects of aloe extracts on wound healing, bone marrow stimulation, and their limited anti-cancer effects. Studies have also provided evidence to suggest that aloe extracts can influence apoptosis and lymphocyte function. The Madagascar species, Aloe vahombe(sic), has been claimed to possess a very wide array of beneficial activities, but this has not been independently confirmed.
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