Hemato-immunologic impact of subchronic exposure to melamine and/or formaldehyde in mice

The aim of the present study was to explore the potential hematotoxic and immunotoxic effects of melamine (MA) in the absence and presence of formaldehyde (FA) in mice. Forty adult Swiss mice were equally allocated into four groups and daily treated with water, MA (50mg/kg), FA (25mg/kg), and MA+FA respectively via feeding needle for 60 consecutive days. Hematological status was evaluated using erythrogram and leukogram profiling. Innate immune functions were assessed by measuring white blood cells lysozyme and phagocytic activities. Serum immunoglobulin levels were evaluated as indicators of humoral immunity. In addition, histologic and immunohistochemical evaluations of splenic tissues were performed. The results indicated that either MA or FA treatment resulted in significant decreases in RBCs, Hb, MCHC, total WBC, lymphocyte, and basophile levels as well as in WBCs phagocytosis and lysozyme activity. In contrast, MCV, PCV%, and reticulocyte levels were significantly increased in these hosts. The total IgM level was significantly reduced in the MA-only-exposed mice but markedly increased in the FA-only-treated ones. A significant decrease in serum IgG levels was detected following either MA or FA treatment. The combined exposure to MA and FA, compared to levels of either toxicant alone, was revealed to evoke a significant improvement in Hb, PCV%, MCV, MCHC, neutrophil, eosinophil, total IgM level, and lysozyme activity; however these values did not reach that of the controls. Furthermore, compared to control mice, both MA-only- and FA-only-treated mice showed a strong distribution of CD4(+) and CD8(+) cells in their spleens, while a moderate presence of the former cells was obvious at their co-exposure. Taken together, these findings revealed that exposure to MA or FA resulted in significant alterations in hemato-immune parameters at variable degrees while a co-exposure resulted in the mitigation of most effects of either toxicant alone.