Breastfeeding has always been recognized as the best way to feed infants, and the World Health Organization recommends exclusive breastfeeding for the first six months of life. In addition to providing nutrients needed for the growth of infants and young children, breast milk can also provide bioactive components such as antibodies and digestive enzymes to help infants resist infections and prevent diseases. The complement system is an important member of the immune system and is made up of a series of complement proteins. The complement system has been discovered since more than 100 years ago, and the study of its activation pathways and functions has mainly focused on the complement components in plasma. Although there are large amounts of complement proteins in breast milk, their function is not well understood. January 18, 2024, Johns Hopkins University, USAWan FengyiThe team of professors (Dr. Xu Dongqing is the first author) is incellThe magazine published a publication entitledcomplement in breast milk modifies offspring gut microbiota to promote infant healthof**,For the first time, the importance of complement components in breast milk was explained. In this article, it was found that the complement in mouse breast milk can selectively kill some specific bacteria in the intestinal tract of young mice and affect the composition of the entire intestinal flora, thereby affecting the resistance of young mice to pathogenic bacterial infection. 
The research team found that wild-type (WT) and complement-deficient toddler mice (C1QC and C3) had different tolerance to infection with the enteric pathogen citrobacter rodentium. To further elucidate why, the researchers conducted a cross-foster experiment and found that all three genotypes of young mice (WT, C1QC and C3) grew up healthy when they were breastfed normally and were able to resist infection with the pathogen citrobacter rodentium. When mice were breastfed with complement deficiency, although they could grow normally, they all showed obvious symptoms such as diarrhea and weight loss when they were infected with citrobacter rodentium, and eventually died. In-depth studies have found that the intestinal microbiota of young mice receiving normal breast milk and complement deficiency breast milk are significantly different, and when different intestinal microbes were transplanted into germ-free (completely sterile) mice, it was found that the intestinal microbiota determined the sensitivity of young mice to citrobacter rodentium infection. The researchers isolated a gram-positive bacterium from the gut microbiota of complement-deficient breastfed mice, identified as belonging to the species Staphylococcus lentus, and found that the response of mice to pathogenic bacterial infections correlated with the abundance of staphylococcus in the gut microbiota. Further in vitro experiments confirmed that in both mouse and human breast milk, Staphylococcus Lentus can activate the entire complement pathway through complement protein C1Q, and eventually form a complement membrane attack complex (MAC), leading to the death of the bacteria themselves. It is worth noting that although previous studies have suggested that the complement activation pathway initiated by the C1Q molecule is antibody-mediated, the research team has experimentally confirmed that the activation of complement and the killing of bacteria in breast milk do not depend on antibodies, but are non-specific innate immune responses. The studyFor the first time, it was discovered that the complement component in breast milk affects children's health and their resistance to external infections by reshaping the intestinal flora of infants and young children, revealing another key active ingredient in breast milk, emphasizing the importance of breastfeeding, and has important guiding significance for the health and growth of infants and young children. 
It is worth mentioning that on January 26, 2024, Harvard Medical School in the United Statesdennis kasperThe research team (Dr. Meng Wu and Dr. Wen Zheng are the co-first authors) are incellThe magazine published a publication entitledgut complement induced by the microbiota combats pathogens and spares commensalsThe study of **, the**It is revealed that there is a separate complement system in the gut that is distinct from the blood complement system. The complement system of the gut can work in harmony with the intestinal symbionts by selectively expressing specific complement components, while acting as a counterweight to pathogens(See: cell |.)Wu Meng, Zheng Wen et al. revealed that the independent complement system in the gut can coexist with intestinal commensal bacteria and fight pathogens).Original link:
2024 Travel Guide