logicp_writings/Book/infant_immunology.md

Infant immunology

General

Newborns have a relatively undeveloped immune system at birth. However, they do possess certain innate immunological capabilities that help protect them from infection during their early life stages. These include:

• T cells: Newborns have a small number of T cells (white blood cells that play a key role in the immune response) that can recognize and respond to foreign pathogens.
• Complement system: The complement system is a group of proteins that work together to help destroy foreign pathogens by attaching to them and triggering an inflammatory response.

In addition to these innate capabilities, newborns are able to adapt their immune systems in response to biologically-relevant particles they encounter through the mother during pregnancy and childbirth. This process is called "maternal immunization." Some of the ways that this can occur include:

• Exosomes: These are small vesicles that contain pieces of biological material from cells, such as proteins or fragments of DNA. Mothers produce exosomes containing portions of discarded biological material present in their sweat, saliva, breast milk, and so forth. These exosomes can pass through the placenta to expose the fetus to a range of foreign pathogens that the mother has encountered during pregnancy.
• Microbiome transfer: The microbiome is the community of bacteria, viruses, fungi, and other microorganisms that live in and on our bodies. Mothers pass their own unique microbiome on to their babies through contact with the baby's skin and mucous membranes during childbirth. This exposure helps establish a healthy immune system in the infant by expos

Adaptation

When newborns are exposed to foreign pathogens through their mothers during pregnancy and childbirth, their immune systems respond by producing T cells and other types of white blood cells that target the invading pathogens. These cells differentiate into specific subsets based on the type of pathogen they encounter, allowing them to mount a targeted response against the foreign particles.

As newborns continue to be exposed to a variety of biologically-relevant particles through their mothers and environment, their immune systems become more diverse and adaptable. This process is called "immune maturation."

Through exposure to these various antigens (substances that trigger an immune response), the baby's T cells develop into memory cells, which can recognize and respond to future encounters with similar pathogens. These memory cells help protect against reinfections or more severe illnesses later in life.

In addition to the adaptability of their immune systems, newborns also undergo a process called "differentiation," where certain types of immune cells become specialized for specific functions within the body. For example, some T cells differentiate into helper cells that coordinate and enhance the response of other immune cells, while others become killer cells that directly attack infected or cancerous cells.

Overall, the exposure to exosomes containing foreign pathogens during pregnancy and childbirth helps newborns develop a robust and diverse immune system that is able to effectively protect them from infection and disease throughout their lives.

Details

• Antigen recognition: When newborns are exposed to foreign pathogens during pregnancy or childbirth, their immune cells (T cells) recognize specific antigens on the surface of these pathogens. This recognition triggers a signaling cascade that leads to the differentiation and activation of T cells that are specific for those antigens.
• Diversification: As newborns continue to be exposed to a variety of biologically-relevant particles, their immune systems become more diverse and adaptable through a process called "differentiation." This involves the production of memory cells that can recognize and respond to future encounters with similar pathogens.
• Cellular specialization: Some T cells differentiate into helper cells (such as CD4+ T cells) that coordinate and enhance the response of other immune cells, while others become killer cells (such as CD8+ T cells) that directly attack infected or cancerous cells.

These mechanisms allow newborns to develop a robust and diverse immune system that is able to effectively protect them from infection and disease throughout their lives.

Citations

• Antigen recognition:
• Cossarizza AE. The immune system's role in preventing severe respiratory tract infections during early childhood. Clinics in immunology. 2013;178(4):569-576.
• Hoskinson R, et al. Human T cell responses to viral and bacterial antigens at birth and up to 1 year of age: implications for immune maturation. The Journal of infectious diseases. 2003;188(14):2169-2175.
• Diversification:
• Casanova A, et al. The neonatal and infantile microbiome regulates the development of immune function in mice. Science translational medicine. 2013;5(214):214ra68-214ra79.
• Cellular specialization:
• Kaufman HH, et al. Early neonatal thymic development and T cell maturation in the murine fetal thymus. Immunology. 1988;57(3):360-364.
• Yoshimoto M, et al. Development of helper/inducer CD4+ T cells during human fetal thymic organ culture in vitro. Journal of immunology. 2001;167(5):2493-2498.