As shown in a new study published in this Wednesday's digital edition of the magazine Nature, the cells that allow bacteria to safely colonize the intestines of newborns also suppress the immune system which causes babies to be more vulnerable to infections.
Scientists of Cincinnati Children's Hospital Medical Centerin the United States, they have investigated the vulnerability of the immune system of babies.
It reaches a world full of viruses
We have always been told that newborns are susceptible to infections because their immune system is immature or underdeveloped. But it seems that this is not entirely true according to this research.
The first days after birth represent a critical period of development in which the immune system of a baby, which must adapt to many of the new stimuli. This includes environmental microbes that are not present in the uterus, but immediately colonize tissues such as the intestine and skin.
"Our findings suggest that infections are caused by immune suppression during this period of development, as opposed to the idea of immaturity of immune cells," summarizes Sing Sing Way, principal investigator and physician in the Division of Infectious Diseases of Children from Cincinnati.
The suppressor cells in this case are CD71 + precursors of mature red blood cell cells.
The researchers found that CD71 + precursor cells they are enriched in newborn mice (and in the blood of the human umbilical cord) to avoid an excessive immune response in babies while adapting to a world full of microbes. CD71 + cells express a enzyme called arginase-2 which is essential to suppress immune cells, a process that plays a vital role in the development of babies' intestines by preventing an attack of the immune system in response to colonizing bacteria that will help digestion and the rest in the future of related functions.
The experiments
The scientists used a series of laboratory tests on human blood cells and mouse models to show that the result of temporary immune suppression in newborns extends beyond the intestines to also affect other parts of the body.
Although vulnerability to newborn infection is well known, Way and his colleagues began their study because previous research had shown that the extent of this compromised immunity in newborn mice varied significantly depending on experimental conditions. This led the authors to the hypothesis that there should be a better explanation about compromised immunity in newborns, than that of immature immune cells.
The scientists transferred immune system cells from adult mice to newborn mice to see if this could increase neonatal immunity during exposure to infections. But, instead of increasing immunity, they saw that the production of protection cytokines The immune system in adult cells faltered in newborn mice, results similar to those observed when adult immune cells were mixed with neonatal cells in laboratory cultures.
In a complementary experiment, the researchers transferred immune system cells from adult mice to newborns exposed to the infection. In adult mice, neonatal immune cells produced the TNF-alpha protective cytokine, It helps the immune system's protective response against infection.
In summary, it seems that we are before another of the mechanisms of human evolution to help our body in its survival in this hostile world that we call home. A mechanism that opens a door to the outside, or rather we could say that it distracts the doorman, so that many of the microorganisms that will be present in our interior can enter the rest of our lives and that will make our journey through life much easier. This entails a "payment" or consequence that is none other than an unprotected exposure to those fat microorganisms that are always in every party.
