Abstract

Background: The imbalance in the T helper (Th) 1/Th2 and Th1/T regulatory (Treg) cells-related immune responses plays a key role in pathogenesis of allergic asthma. Objectives: The aim of this study was to evaluate the effects of CPG-Oligodeoxynucleotide (CPG-ODN), Monophosphoryl Lipid A (MPLA) and Bacillus Calmette-Guerin (BCG) on the ratio of Th1/Th2 and Th1/Treg cells-related parameters in an animal model of asthma. Methods: This was an experimental study in which female BALB/c mice were divided to five groups and then immunized Subcutaneously (SC) with the allergen Dermatophagoides pteronyssinus 2 (Derp2) on days 1, 15 and 22. Three groups of mice were considered as test groups and pre-treated SC with CPG, CPG + MPLA or CPG + BCG on days 0, 14 and 21. Two groups were also considered as saline-control group and Derp2-sensitized control group that were administrated only saline or allergen Derp2, respectively. The mice (except saline-control group) were challenged intranasally with allergen Derp2 for ten days, from days 28 to 37 of post immunization. Blood samples were obtained from retro-orbital sinus, on days 0, 23 and 40. The serum Interleukin (IL)-4, Interferon (IFN)- , Immunoglobulin (Ig) E and IgG2a levels were measured using the enzyme linked immunosorbent assay (ELISA) technique. The blood count of Th1- and Treg cells was detected using flow cytometry. Results: At sensitization phase, the serum IFN- /IL4 ratio was significantly increased in Derp2-sensitized group pre-treated with CPG plus MPLA or CPG plus BCG as compared with Derp2-sensitized control mice (P < 0.002 and P < 0.003). The IFN- /IL4 ratio was also markedly elevated in Derp2-sensitized group pre-treated with CPG as compared with Derp2-sensitized control mice (P = 0.07). In the challenge phase, the IFN- /IL4, IgG2a/IgE and Th1/Treg ratios in Derp2-sensitized mice pre-treated with CPG plus MPLA were significantly higher than in Derp2-sensitized control mice (P < 0.003, P < 0.006 and P < 0.003, respectively). The IFN- /IL4 and Th1/Treg ratios were also significantly raised in Derp2-sensitized mice pre-treated with CPG plus BCG in comparison with Derp2- sensitized control mice (P < 0.001 and P = 0.012, respectively). In the challenge phase the Th1/Treg ratio was significantly decreased in Derp2-sensitized group pre-treated with CPG plus BCG in comparison with Derp2-sensitized mice pre-treated with CPG (P = 0.011). The Th1/Treg ratio in Derp2-sensitized group pre-treated with CPG plus MPLA was significantly higher than in Derp2-sensitized mice pre-treated with CPG plus BCG (P < 0.035). Conclusions: These results showed that BCG, MPLA and CPG improve the Th1/Th2- and Th1/Treg cells imbalances in a mouse model of asthma.

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