Our immune system is our main line of defence against infectious diseases. It identifies antigens and eliminates them before they can do major damage to the body. Memory cells in our immune system remember these pathogens so antibodies can be quickly formed if the same one attacks the body again.
There are two arms of the immune system, namely the innate immune system (the one we are born with) and the adaptive immune system (the one we acquire as we grow older).
Newborns are highly susceptible to infections since they are not exposed to any pathogen inside the womb. However, as soon as a baby is born, they are faced with many pathogens that are totally new to their immune system. To deal with them, their immune system should develop quickly.
The developmental pathway of the immune system is considered to be a major determinant of overall health later in life. However, not much is known about the molecular mechanisms involved in this development.
Now, a group of researchers in the USA say that they have determined how the immune system of neonates develops within the first week of life.
The findings of the study, published in the journal Frontiers in Immunology, indicate that such an understanding of the immune system can help develop precision vaccines for newborns to save more lives.
Precision vaccination is a concept based on the fact that every individual has different susceptibility to diseases based on their genes, age, sex and environmental factors. These factors would determine how one reacts to vaccines too.
Experts suggest that the factors should be taken into account while developing new vaccines so the vaccines can be optimised to highly vulnerable individuals such as newborns, the elderly and those with chronic diseases.
For the study, the researchers looked into the proteins present in the plasma (blood without RBCs, WBCs, platelets and other cellular components) of two groups of newborns - 30 neonates from The Gambia and 19 from Papua New Guinea - born through vaginal birth.
Plasma samples were taken on the day of birth, and on the first, third and seventh day of life. A significant increase was noted in acute phase proteins on day 1 after birth. Acute-phase proteins are those that generally increase in response to inflammation.
Here are some of the findings of the study:
There was an increase in haptoglobin within the first 24 hours after birth. Haptoglobin (HP) is a type of acute-phase protein that clears free haemoglobin from the circulation and helps recycle iron and prevent kidney toxicity that may occur when this free hemoglobin passes through kidneys. The binding of HP with haemoglobin mediates an anti-inflammatory and antioxidant effect. HP levels are raised in newborns with bacterial infections. However, their exact role in sepsis remains unknown.
SAA1 is yet another acute-phase protein that was found to be increased on day 1 after birth. This protein is known to have antimicrobial activity and its levels increase in response to infections. SSA1 levels were found to be reduced to day-zero levels by day three and seven.
Complement system components were also found to be increased as early as 24 hours after birth. The complement system is a part of the innate immune system and is responsible for direct destruction of pathogens. On the other hand, complement inhibitors decrease steadily over the first week and then start rising on day seven.
Maternal antibodies decline over the first week while antibodies related to the complement pathway increase.
The authors suggested that even though their findings are not surprising, the research was done with a small sample obtained from geographically distinct areas. The study shows that newborns everywhere have a particularly consistent trajectory of immune system development in the first week of life and that high quality and reproducible evidence can be obtained even in resource-limited settings.
For more information, read our article on Immune system and Immunity.
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