Riboflavin, or
vitamin B2, as a precursor of the
coenzymes FAD and
FMN, has an indirect influence on many metabolic processes and determines the proper functioning of several systems, including the immune system. In the human population, plasma
riboflavin concentration varies from 3·1 nM (in a moderate deficiency, e.g. in pregnant women) to 10·4 nM (in healthy adults) and 300 nM (in cases of
riboflavin supplementation). The purpose of the present study was to investigate the effects of
riboflavin concentration on the activity and viability of macrophages, i.e. on one of the immunocompetent cell populations. The study was performed on the murine monocyte/macrophage RAW 264.7 cell line cultured in medium with various
riboflavin concentrations (3·1, 10·4, 300 and 531 nM). The results show that
riboflavin deprivation has negative effects on both the activity and viability of macrophages and reduces their ability to generate an immune response. Signs of
riboflavin deficiency developed in RAW 264.7 cells within 4 d of culture in the medium with a low
riboflavin concentration (3·1 nM). In particular, the low
riboflavin content reduced the proliferation rate and enhanced apoptotic cell death connected with the release of
lactate dehydrogenase. The
riboflavin deprivation impaired cell adhesion, completely inhibited the respiratory burst and slightly impaired phagocytosis of the
zymosan particles. In conclusion, macrophages are sensitive to
riboflavin deficiency; thus, a low
riboflavin intake in the diet may affect the immune system and may consequently decrease proper host immune defence.