Immunoglobulin: Types, Functions, Role in Baby’s Immunity, and Importance for Newborns
Introduction
• The human body is equipped with a remarkable defense system known as the immune system. One of its most critical components is immunoglobulins—specialized proteins that detect and neutralize harmful pathogens such as bacteria, viruses, and toxins.
• For newborns, whose immune systems are still developing, immunoglobulins play an even more essential role. Babies rely heavily on the immunoglobulins transferred from their mothers during pregnancy and through breast milk after birth. These antibodies provide protection during the vulnerable early months of life, acting as a shield until the baby’s immune system becomes strong enough to defend itself.
• This article explores the types of immunoglobulins, their functions, their role in newborn immunity, and why they are so important for early life health.
What Are Immunoglobulins?
• Immunoglobulins (Ig) are glycoproteins produced mainly by B lymphocytes (a type of white blood cell) in response to foreign substances known as antigens.
• When an antigen enters the body—such as a virus or bacteria—immunoglobulins bind to it, marking it for destruction by other immune cells. This is part of the body’s adaptive immune response, which remembers past infections and responds faster to future threats.
• Immunoglobulins are also known as antibodies and circulate in the blood, lymph, and other body fluids.
Types of Immunoglobulins and Their Functions
There are five main classes of immunoglobulins in humans, each with specific roles:
1. Immunoglobulin G (IgG)
• Most abundant antibody in the blood (about 70–80% of total antibodies).
• Can cross the placenta during pregnancy, providing passive immunity to the fetus.
• Protects against bacterial and viral infections.
• Plays a role in long-term immunity after vaccination or infection.
Functions:
• Neutralizes toxins and viruses.
• Activates the complement system (a group of proteins that aids immune defense).
• Provides lasting immunity after infection.
2. Immunoglobulin A (IgA)
• Found in mucosal secretions such as saliva, tears, respiratory tract, digestive tract, and breast milk.
• Protects body surfaces exposed to external environments.
Functions:
• Prevents pathogens from attaching to mucosal surfaces.
• Plays a major role in protecting the baby’s digestive tract through breastfeeding.
3. Immunoglobulin M (IgM)
• The first antibody produced during an initial immune response.
• Found in blood and lymphatic fluid.
Functions:
• Provides early defense against infections before IgG production ramps up.
• Efficient at forming complexes with antigens.
4. Immunoglobulin E (IgE)
• Involved in allergic reactions and defense against parasites.
• Present in very low levels in normal blood.
Functions:
• Triggers release of histamine and other chemicals from mast cells.
• Plays a protective role against parasitic worms.
5. Immunoglobulin D (IgD)
• Found in small amounts in blood and on the surface of immature B cells.
• Exact role not fully understood.
Functions:
Helps initiate B-cell activation in immune responses.
How Immunoglobulins Provide Immunity to Babies
Newborns are particularly vulnerable to infections because their immune systems are immature. However, nature has designed a way to protect them—through passive immunity provided by their mothers.
1. Immunity Before Birth (Prenatal Passive Immunity)
• IgG antibodies from the mother cross the placenta during the third trimester.
• This transfer provides the newborn with immunity against diseases the mother has already encountered or been vaccinated against.
2. Immunity After Birth (Postnatal Passive Immunity)
• Breast milk, especially colostrum (the thick, yellowish milk produced in the first few days after delivery), is rich in IgA antibodies.
• These antibodies coat the baby’s digestive tract and protect against infections.
• Breastfeeding continues to supply immunoglobulins for as long as the baby is nursed.
Importance of Immunoglobulins for Newborn Health
Immunoglobulins are vital for newborn survival and health because:
• Protect Against Infections: Babies can’t yet mount strong immune responses, so antibodies provide early defense.
• Support Gut Health: IgA in breast milk prevents harmful bacteria from damaging the baby’s intestinal lining.
• Reduce Risk of Allergies: Early exposure to maternal antibodies may help regulate immune development.
• Aid in Vaccine Effectiveness: Maternal antibodies protect until the baby can receive vaccinations.
• Prevent Serious Illness: IgG shields against life-threatening diseases during the first months.
Medical Uses of Immunoglobulins in Newborn Care
• Sometimes, newborns may require immunoglobulin therapy, especially in cases of:
• Premature birth (less time for IgG transfer in the womb).
• Immune deficiencies.
• Rh incompatibility between mother and baby (anti-D immunoglobulin is used to prevent hemolytic disease of the newborn).
Factors That Can Affect Immunoglobulin Levels in Newborns
Prematurity: Less IgG transfer occurs before 37 weeks.
• Maternal infections: Can impact the quality and quantity of antibodies.
• Malnutrition in mother: Affects immune protein production.
• Breastfeeding duration: Longer breastfeeding provides prolonged antibody support.
Boosting Immunity in Newborns
• Ensure maternal vaccinations during pregnancy (e.g., tetanus, influenza).
• Exclusive breastfeeding for at least the first 6 months.
• Good maternal nutrition for healthy antibody production.
• Timely infant vaccinations to build active immunity.
Frequently Asked Questions (FAQs)
Q1: Can formula milk provide immunoglobulins like breast milk?
No, infant formula does not naturally contain active antibodies like breast milk. Breast milk contains living immune factors, especially IgA.
Q2: How long do maternal IgG antibodies last in a newborn?
Maternal IgG typically lasts about 3–6 months after birth, after which the baby’s own immune system takes over.
Q3: Is colostrum more important than regular breast milk?
Yes, colostrum is especially rich in antibodies, particularly IgA, and provides a concentrated immune boost in the first few days after birth.
Q4: Can immunoglobulin therapy be given to newborns?
Yes, in certain medical conditions such as immune deficiencies or severe infections, doctors may prescribe intravenous immunoglobulin (IVIG).
Conclusion
• Immunoglobulins are the cornerstone of immunity—protecting the body from harmful pathogens and ensuring long-term health. For newborns, they are a lifeline during the early months of life when the immune system is still under development.
• Through the transfer of IgG before birth and IgA through breastfeeding, mothers provide their babies with powerful immune protection. This natural defense helps prevent infections, supports healthy development, and gives babies the best possible start in life.
• By understanding the role and importance of immunoglobulins, parents can make informed choices—such as prioritizing maternal health, ensuring timely vaccinations, and supporting breastfeeding—to protect their little ones.
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Writer: Vandita Singh, Lucknow (GS India Nursing Group)