Immunomodulatory effect of Moringa peregrina leaves, ex vivo and in vivo study

This study was conducted to assess the in vivo and ex vivo immunomodulatory effect of the ethanol leaves extract of Moringa peregrina in Balb/c mice. For this study, five groups of 5 Balb/c mice were given a single acute subtoxic oral dose of the ethanolic extract at 1.13, 11.30, 23.40 and 113.4 mg/kg and the immunomodulatory effect was assessed on the 6^th day following the ingestion. In the (non-functional) assessment, the effect of the extract on the body weight, relative lymphoid organ weight, splenic cellularity and peripheral blood hematologic parameters were evaluated. While in the immunomodulation assessment (functional), we investigated the effect of the extract on the proliferative capacity of splenic lymphocytes and peripheral T and B lymphocytes using mitogen blastogenesis, mixed allogeneic MLR and IgM-Plaque forming cells assays. The ingestion of M. peregrina extract caused a significant increase in the body weight, weight and number of cells of spleen and lymph nodes of the treated mice. Furthermore, the count of RBCs, WBCs, platelets, hemoglobin concentration and PCV % were increased by the extract treatment in a dose-dependent manner. M. peregrina enhanced the proliferative responses of splenic lymphocytes for both T cell and B-cell mitogens. Likewise, the mixed lymphocyte reaction MLR assay has revealed a T-cell dependent proliferation enhancement in the extract treated mice. Moreover, the oral administration of M. peregrina leaves extracts significantly increased PFCs/10⁶ splenocytes in a dose-dependent manner. In conclusion, subtoxic acute doses of M. peregrina extract demonstrated significant potential as an immunomodulatory agent even at the lowest dose of 1.13 mg/kg.

Dibenzo[def,p]chrysene (DBC) suppresses antibody formation in spleen cells following oral exposures of mice

Dibenzo[def,p]chrysene (DBC) is a potent environmental carcinogen in rodents, fish, and human cells examined in culture. There are numerous similarities between the patterns of cytochrome P-450 (P450) activation of DBC and its covalent binding to DNA and proteins with another polycyclic aromatic hydrocarbon (PAH), 7,12-dimethylbenz[a]anthracene (DMBA). Our lab has previously shown that DMBA produces immunosuppression in rodents and human cell systems. Therefore, the purpose of these studies was to examine the immunotoxicity of DBC in a rodent model that was found to be sensitive to the immunosuppressive effects of DMBA. Data showed that DBC had similar potency to DMBA in producing suppression of a T-dependent antibody response (TDAR) and altered spleen cell subsets in a similar manner as DMBA when DMBA was given by gavage for 5 d in corn oil to mice at doses of 1-100 mg/kg total cumulative doses. T-cell-independent antigen (TNP-Ficoll) responses were quantitatively less sensitive to DBC suppression. It was also found that as with DMBA, DBC produced a persistent immunosuppression, which lasted for at least 4 wk following dosing with a novel pill method for self-administration of DBC. In conclusion, DBC appears to possess many of the same characteristics of DMBA in terms of its immunotoxicity.

The Downstream Transcriptional Enhancer, Ed, positively regulates mouse Ig kappa gene expression and somatic hypermutation

The mouse Igkappa locus has three known transcriptional enhancers: the matrix association region/intronic enhancer, the 3' enhancer (E3'), and the further downstream enhancer (Ed). Previous studies have shown that both matrix association region/intronic and E3' enhancers are required for maximal gene rearrangement of the locus, and that E3' is also required for maximal expression and somatic hypermutation (SHM). To functionally elucidate Ed in vivo, we generated knockout mice with a targeted germline deletion of Ed. Ed deleted homozygous mice (Ed-/-) have moderately reduced numbers of Igkappa expressing B cells and correspondingly increased numbers of Iglambda expressing B cells in spleen. Ed-/- mice also have decreased Igkappa mRNA expression in resting and T cell-dependent activated splenic B cells and reduced Igkappa chains in sera. However, our analysis indicates that Igkappa gene rearrangement is normal in Ed-/- mice. In addition, our results show that Ed-/- mice exhibit reduced SHM in the Igkappa gene J-C intronic region in germinal center B cells from Peyer's patches. We conclude that Ed positively regulates Igkappa gene expression and SHM, but not gene rearrangement.

Cytochrome P450 1B1 Is Required for 7,12-Dimethylbenz(a)-anthracene (DMBA) Induced Spleen Cell Immunotoxicity

7,12-Dimethylbenz(a)anthracene (DMBA) is a potent carcinogen that induces immunosuppression of both humoral and cell-mediated immunity in mice and other species. Previous studies have shown that CYP1B1 is required for bone marrow toxicity produced by DMBA in mice. Therefore, the purpose of these studies was to determine whether CYP1B1 was required for spleen cell immunotoxicity. Female C57BL/6N wild-type (WT) and CYP1B1 knockout (-/-) mice were treated with 0, 17, 50, or 150 mg/kg (cumulative dose) DMBA in corn oil by oral gavage once a day for five days. Several immunotoxicological assays were used to assess the effects of DMBA on systemic immunity. These included the in vitro T-dependent antibody response to sheep red blood cells (SRBC) measured using a direct plaque forming cell (PFC) assay, T- and B-cell mitogenesis induced by Con A and LPS, and nonspecific cell-mediated immunity was evaluated using an NK cytotoxicity assay. In addition, lymphocyte subpopulations were measured by flow cytometry using specific cell surface markers. Following five days of DMBA treatment, the body weights and spleen cell surface markers of the WT and CYP1B1 (-/-) mice showed no significant changes. A decrease in NK activity was found at the 50 mg/kg DMBA dose in WT mice, but not in the CYP1B1 (-/-) mice. Interestingly, at the 150 mg/kg dose of DMBA, CYP1B1 null mice had decreased NK activity, whereas WT mice did not. The SRBC PFC response demonstrated that the IgM antibody response was suppressed by DMBA in WT mice in a dose-dependent manner (significant at 50 and 150 mg/kg). However, there were no changes in the SRBC PFC responses in any DMBA test group in the CYP1B1 (-/-) mice. Similarly, while DMBA suppressed B- and T-cell mitogenesis at the 50 and 150 mg/kg dose levels in C57BL/6N WT mice, no effect was seen in CYP1B1 (-/-) mice. Thus, CYP1B1 appears to be critical for the immunosuppression of DMBA in mice, suggesting a role for bioreactive metabolites in the spleen cell immunotoxicity produced by DMBA.