Glycolipid sensing and innate immunity in paracoccidioidomycosis.

Distinct glycolipid profiles are described in microorganisms, which have been shown to modulate the innate immune system. We tested the hypothesis that glycosphingolipids from Paracoccidioides brasiliensis have immunomodulatory properties on monocytes and dendritic cells of two groups of healthy individuals, one cured of paracoccidioidomycosis in the past (CUR-I) and the other nonexposed to P. brasiliensis (HNE-I). Two classes of glycosphingolipids purified from yeast cells were evaluated: a neutral glycosphingolipid, monohexosylceramide (CMH), and acidic glycosylinositolphosphorylceramides (GIPCs). Both glycosphingolipids affected the functioning of innate immunity cells, interfering with the antigen presenting process: P. brasiliensis yeast cells phagocytosis, IL-10 secretion, and costimulatory molecules and recognition receptors expression by monocytes were altered, while dendritic cell antigen presentation to autologous T cells was markedly down-modulated as shown by reduced T-cell proliferative responses. The mechanisms by which CMH and GIPCs exert their effects differ since the target cells did not always respond similarly to the challenge with the glycosphingolipids. Moreover, CUR-I and HNE-I presented different responses to the glycosphingolipids. Differences not only in the glycosphingolipid structure (such as the polar head group or the ceramide moiety), but also in the innate immunity properties of CUR-I and HNE-I, may underlie these differences and contribute to individual's susceptibility or resistance to develop paracoccidioidomycosis.

Soy lecithin supplementation alters macrophage phagocytosis and lymphocyte response to concanavalin A: a study in alloxan-induced diabetic rats.

Dietary soy lecithin supplementation decreases hyperlipidemia and influences lipid metabolism. Although this product is used by diabetic patients, there are no data about the effect of soy lecithin supplementation on the immune system. The addition of phosphatidylcholine, the main component of lecithin, to a culture of lymphocytes has been reported to alter their function. If phosphatidylcholine changes lymphocyte functions in vitro as previously shown, then it could also affect immune cells in vivo. In the present study, the effect of dietary soy lecithin on macrophage phagocytic capacity and on lymphocyte number in response to concanavalin A (ConA) stimulation was investigated in non-diabetic and alloxan-induced diabetic rats. Supplementation was carried out daily with 2 g kg(-1) b.w. lecithin during 7 days. After that, blood was drawn from fasting rats and peritoneal macrophages and mesenteric lymph node lymphocytes were collected to determine the phospholipid content. Plasma triacylglycerol (TAG), total and HDL cholesterol and glucose levels were also determined. Lymphocytes were stimulated by ConA. The MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) dye reduction method and flow cytometry were employed to evaluate lymphocyte metabolism and cell number, respectively. Soy lecithin supplementation significantly increased both macrophage phagocytic capacity (+29%) in non-diabetic rats and the lymphocyte number in diabetic rats (+92%). It is unlikely that plasma lipid levels indirectly affect immune cells, since plasma cholesterol, TAG, or phospholipid content was not modified by lecithin supplementation. In conclusion, lymphocyte and macrophage function were altered by lecithin supplementation, indicating an immunomodulatory effect of phosphatidylcholine.