Effect of methanol intoxication on rat neutrophil functions

Methanol (MeOH) toxicity, a potential problem from accidental, intentional, as well as occupational and daily ingestion of the agent, receives attention only after severe signs of intoxication have set in or death is imminent. While accidental and intentional exposures involve high doses, the occupational and ingestion forms more often reflect small daily intakes. Still, even at these low levels, little is known about the potential immunotoxic implications from these recurring exposures. As innate immunity confers a first-line of defense against infection, a study was designed to examine the effects of daily exposure to MeOH (at (1)/(4) LD(50) level, for up to 15 or 30 days) on neutrophil (PMN) functions using rats that were (or were not) injected with sheep red blood cells (SRBC) during the course of exposures. Blood samples were analyzed for total (TLC) and differential leucocyte counts (DLC), and isolated neutrophils (PMN) were assessed for changes in function by monitoring phagocytic (PI) and avidity indices (AI), nitroblue tetrazolium (NBT) reduction, and adherence. Body weights were monitored during exposures and weights of major immune system organs (i.e., spleen, thymus, lymph nodes) were assessed at sacrifice. Body and organ weight, TLC, blood PMN levels, PMN PI, and adherence were all significantly decreased in SRBC-untreated rats that received MeOH, although these cells did also display significant increases in AI and NBT reduction. With SRBC-treated rats, though the percentage of PMN in the blood increased with ongoing MeOH exposure, all the other parameters were markedly decreased in comparison to their controls. Thus, this study showed that repeated exposures to MeOH modulates PMN functions, thereby potentially altering the first line of defense in a normal immune response in exposed hosts.