Immunology of Aloe vera
This first study supports the fact that Aloe protects the skin cells (keratinocytes or squamous cells) from immunosuppression of UV light. These are the same types of cells that cover the vagina and cervix of the uterus. This general protective effect of the polysaccharides of Aloe may play a part in the induction of an immune response to viruses such as HPV as further suggested by other studies.
Photochem Photobiol 1999 Feb;69(2):141-7:
Inhibition of UV-induced immune suppression and interleukin-10 production by plant oligosaccharides and polysaccharides.
Strickland FM, Darvill A, Albersheim P, Eberhard S, Pauly M, Pelley RP. Department of Immunology, University of Texas M.D. Anderson Cancer Center, Houston 77030, USA.
"Application of Aloe barbadensis poly/oligosaccharides to UV-irradiated skin prevents photosuppression of delayed-type hypersensitivity (DTH) responses in mice. We tested the hypothesis that these carbohydrates belong to a family of biologically active, plant-derived polysaccharides that can regulate responses to injury in animal tissues. C3H mice were exposed to 5 kJ/m2 UVB from unfiltered FS40 sunlamps and treated with between 1 pg and 10 micrograms tamarind xyloglucans or control polysaccharides methylcellulose or dextran in saline. The mice were sensitized 3 days later with Candida albicans.
Tamarind xyloglucans and purified Aloe poly/oligosaccharides prevented suppression of DTH responses in vivo and reduced the amount of interleukin (IL)-10 observed in UV-irradiated murine epidermis. Tamarind xyloglucans were immunoprotective at low picogram doses. In contrast, the control polysaccharides methylcellulose and dextran had no effect on immune suppression or cutaneous IL-10 at any dose.
Tamarind xyloglucans and Aloe poly/oligosaccharides also prevented suppression of immune responses to alloantigen in mice exposed to 30 kJ/m2 UVB radiation. To assess the effect of the carbohydrates on keratinocytes, murine Pam212 cells were exposed to 300 J/m2 UVB radiation and treated for 1 h with tamarind xyloglucans or Aloe poly/oligosaccharides.
Treatment of keratinocytes with immunoprotective carbohydrates reduced IL-10 production by approximately 50% compared with the cells treated with UV radiation alone and completely blocked suppressive activity of the culture supernatants in vivo. The tamarind xyloglucans also blocked UV-activated phosphorylation of SAPK/JNK protein but had no effect on p38 phosphorylation. These results indicate that animals, like plants, may use carbohydrates to regulate responses to environmental stimuli."
Immunol Lett. 2006 Jun 15;105(2):101-14.
Polysaccharide biological response modifiers.
Leung MY, Liu C, Koon JC, Fung KP. Institute of Chinese Medicine, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, People's Republic of China.
“Biological response modifiers (BRMs) are substances which augment immune response. BRMs can be cytokines which are produced endogenously in our body by immune cells or derivatives of bacteria, fungi, brown algae, Aloe vera and photosynthetic plants. Such exogeneous derivatives (exogeneous BRMs) can be nucleic acid (CpG), lipid (lipotechoic acid), protein or polysaccharide in nature. The receptors for these exogeneous BRMs are pattern recognition receptors. The binding of exogeneous BRMs to pattern recognition receptors triggers immune response. Exogenous BRMs have been reported to have anti-viral, anti-bacterial, anti-fungal, anti-parasitic, and anti-tumor activities. Among different exogeneous BRMs, polysaccharide BRMs have the widest occurrence in nature. Some polysaccharide BRMs have been tested for their therapeutic properties in human clinical trials. An overview of current understandings of polysaccharide BRMs is summarized in this review.”
Glycobiology. 2004 Jun;14(6):501-10.
Chemical and biological characterization of a polysaccharide biological response modifier from Aloe vera L. var. chinensis (Haw.)
Berg.Leung MY, Liu C, Zhu LF, Hui YZ, Yu B, Fung KP. Institute of Chinese Medicine, Chinese University of Hong Kong, Shatin, N.T., Hong Kong, People's Republic of China.
“Three purified polysaccharide fractions designated as PAC-I, PAC-II, and PAC-III were prepared from Aloe vera L. var. chinensis (Haw.) Berg. by membrane fractionation and gel filtration HPLC. The polysaccharide fractions had molecular weights of 10,000 kDa, 1300 kDa, and 470 kDa, respectively. The major sugar residue in the polysaccharide fractions is mannose, which was found to be 91.5% in PAC-I, 87.9% in PAC-II, and 53.7% in PAC-III. The protein contents in the polysaccharide fractions was undetectable. NMR study of PAC-I and PAC-II demonstrated the polysaccharides shared the same structure. The main skeletons of PAC-I and PAC-II are beta-(1-->4)-D linked mannose with acetylation at C-6 of manopyranosyl. The polysaccharide fractions stimulated peritoneal macrophages, splenic T and B cell proliferation, and activated these cells to secrete TNF-alpha, IL-1 beta, INF-gamma, IL-2, and IL-6. The polysaccharides were nontoxic and exhibited potent indirect antitumor response in murine model. PAC-I, which had the highest mannose content and molecular weight, was found to be the most potent biological response modifier of the three fractions. Our results suggested that the potency of aloe polysaccharide fraction increases as mannose content and molecular weight of the polysaccharide fraction increase.”
Carbohydr Res. 2006 Feb 27;341(3):355-64.
Novel bioactive maloyl glucans from aloe vera gel: isolation, structure elucidation and in vitro bioassays.
Esua MF, Rauwald JW. Wolfenbuetteler Strasse 25c, 30519 Hannover, and University of Leipzig, Institute of Pharmacy, Leipzig, Germany.
“In this study, three novel maloyl glucans were isolated at temperatures below 15 degrees C from aloe vera gel (Aloe barbadensis Miller). These compounds were characterized using NMR spectroscopy, ESIMS, MALDITOF-MS and capillary electrophoresis. The compounds were characterized as 6-O-(1-L-maloyl)-alpha-,beta-D-Glcp (veracylglucan A), alpha-D-Glcp-(1-->4)-6-O-(1-L-maloyl)-alpha,-beta,-D-Glcp (veracylglucan B) and alpha-D-Glcp-(1-->4)-tetra-[6-O-(1-L-maloyl)-alpha-D-Glcp-(1-->4)]-6-O-(1-L-maloyl)-alpha,-beta-D-Glcp (veracylglucan C). These unusual malic acid acylated carbohydrates were then tested in vitro for effects on cell proliferation and gene expression of proinflammatory cytokines, IL-6, IL-8 and ICAM-1, using RT-PCR. Veracylglucan B demonstrated potent anti-inflammatory and anti-proliferative effects, while Veracylglucan C, on the other hand, exhibited significant cell proliferative and anti-inflammatory activities. Veracylglucan A could only be isolated in smaller quantities, and it proved to be very unstable. Thus no biological effects could be observed in this respect. The in vitro bioassays also indicated that Veracylglucan B and C are antagonistic and competitive in their effects on cell proliferation. The results of this work represent a major step forward in the research on aloe vera gel. This is the first time that two fully chemically characterized compounds are shown to be responsible for known biological activities of aloe vera gel.”
Int J Immunopharmacol. 1988;10(8):967-74.
Enhancement of allo-responsiveness of human lymphocytes by acemannan (Carrisyn).
Womble D, Helderman JH. Renal Immunology Laboratory, University of Texas Southwestern Medical Center, Dallas.
“Healing powers have been imputed as being a feature of the gel from the aloe vera plant for centuries. The recent isolation of the active ingredient, acemannan, has made testing of this drug important. Since the drug appears to enhance monocyte function in other experiments, these studies were designed to test the capacity of acemannan to enhance immune response to alloantigen and to test whether the potential enhancement is a monocyte driven phenomenon. Acemannan did not enhance lymphocyte response to syngeneic antigens in the mixed lymphocyte culture (MLC) but importantly increased alloantigenic response in a dose-response fashion (2.6 x 10(-7) - 2.6 x 10(-9)M). This effect of acemannan was shown to be a specific response and to concur with concentrations of in vitro acemannan achievable in vivo. A separate series of mixing experiments demonstrated that acemannan incubation with monocytes permitted monocyte driven signals to enhance T-cell response to lectin. It is concluded that acemannan, the active ingredient of the aloe vera plant, is an important immunoenhancer in that it increases lymphocyte response to alloantigen. It is suggested that the mechanism involves enhancement of monocyte release of IL-I under the aegis of alloantigen. This mechanism may explain in part the recently observed capacity of acemannan to abrogate viral infections in animal and man.”
Nat Immun 1998, 16:1, 27-33
Biotherapy with the pineal immunomodulating hormone melatonin versus melatonin plus aloe vera in untreatable advanced solid neoplasms.
Lissoni P; Giani L; Zerbini S; Trabattoni P; Rovelli F Division of Radiation Oncology, San Gerardo Hospital, Monza, Milan, Italy.
“The possibility of natural cancer therapy has been recently suggested by advances in the knowledge of tumor immunobiology. Either cytokines such as IL-2, or neurohormones, such as the pineal indole melatonin (MLT), may activate anticancer immunity. In addition, immunomodulating substances have also been isolated from plants, particularly from Aloe vera. Preliminary clinical studies had already shown that MLT may induce some benefits in untreatable metastatic solid tumor patients, whereas, for the time being, no clinical trial has been performed with aloe products. We have carried out a clinical study to evaluate whether the concomitant administration of aloe may enhance the therapeutic results of MLT in patients with advanced solid tumors for whom no effective standard anticancer therapies are available. The study included 50 patients suffering from lung cancer, gastrointestinal tract tumors, breast cancer or brain glioblastoma, who were treated with MLT alone (20 mg/day orally in the dark period) or MLT plus A. vera tincture (1 ml twice/day). A partial response (PR) was achieved in 2/24 patients treated with MLT plus aloe and in none of the patients treated with MLT alone. Stable disease (SD) was achieved in 12/24 and in 7/26 patients treated with MLT plus aloe or MLT alone, respectively. Therefore, the percentage of nonprogressing patients (PR + SD) was significantly higher in the group treated with MLT plus aloe than in the MLT group (14/24 vs. 7/26, p < 0.05). The percent 1-year survival was significantly higher in patients treated with MLT plus aloe (9/24 vs. 4/26, p < 0.05). Both treatments were well tolerated. This preliminary study would suggest that natural cancer therapy with MLT plus A. vera extracts may produce some therapeutic benefits, at least in terms of stabilization of disease and survival, in patients with advanced solid tumors, for whom no other standard effective therapy is available.”
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