Colostrum: Why Mother's First Milk Gives Babies Immunity (IgA)
Biology · Human Health and Diseases · NEET
Colostrum is the yellowish fluid a mother makes in the first few days of feeding. It has plenty of the antibody IgA, which protects the newborn baby's gut. Because the baby gets ready-made antibodies (it does not make them itself), this is passive immunity. Memory hook: "First milk = IgA = a free gift of protection."
A baby receives ready-made antibodies from the mother in two ways: IgG crosses the placenta before birth, and IgA comes through colostrum after birth. Both are passive immunity.
Your doubts, answered
Which antibody is present in colostrum?
Colostrum is rich in IgA. NCERT says the yellowish colostrum secreted during the initial days of lactation has abundant antibodies to protect the infant, and the specific antibody is IgA. In NEET, if the question asks 'colostrum contains which immunoglobulin', the answer is always IgA.
Is colostrum an example of active or passive immunity?
It is passive immunity. The baby receives ready-made antibodies (IgA) from the mother's milk; the baby does not make these antibodies itself. Passive immunity means antibodies are given from outside, so there is no memory and the protection is short-lived.
What is the difference between IgA in colostrum and IgG across the placenta?
Both give the baby passive immunity, but at different times. IgG crosses the placenta before birth (from mother's blood to the foetus). IgA is passed after birth through colostrum and breast milk, and it protects the baby's gut lining. For NEET, remember: placenta = IgG (before birth), colostrum = IgA (after birth).
Why is colostrum yellow and why do doctors recommend it?
Colostrum is yellowish because it is thick and rich in antibodies and nutrients. Doctors recommend early breast-feeding because colostrum gives the newborn several antibodies that build resistance before the baby's own immune system matures. This is why 'breast-feeding in the initial days' is linked to a healthy baby in NEET assertion-reason questions.
Does colostrum contain white blood cells like macrophages?
Colostrum does contain some cells, but the reason it imparts immunity in NEET answers is the antibody IgA, not cells. In the 2019 PYQ the options included natural killer cells, monocytes and macrophages, but the correct answer is Immunoglobulin A. Choose the antibody, not the cell.
⚠️ The NEET trap ✗ Picking 'macrophages' or 'natural killer cells' when asked why colostrum protects the newborn. ✓ The protective factor in colostrum is the antibody Immunoglobulin A (IgA), not any cell. 🧠 The question says 'imparts immunity' — in NEET that means antibody. Colostrum = IgA. Cells (NK, monocytes, macrophages) belong to innate immunity, not to why colostrum works.
Real NEET questions
NEET 2019
Colostrum, the yellowish fluid secreted by mother during the initial days of lactation, is very essential to impart immunity to the new born infants because it contains:
A · Natural killer cells
B · Monocytes
C · Macrophages
D · Immunoglobulin A ✓
Solution: NCERT states that colostrum has abundant antibodies (IgA) to protect the infant. Because ready-made antibodies are transferred to the newborn, this is passive immunity. Natural killer cells, monocytes and macrophages are cells of innate immunity, not the protective factor colostrum provides — so the answer is Immunoglobulin A.
NEET 2020
Identify the wrong statement with reference to immunity.
A · Active immunity is quick and gives full response ✓
B · Foetus receives some antibodies from mother, it is an example for passive immunity
C · When exposed to antigen antibodies are produced in the host's body. It is called Active immunity
D · When ready-made antibodies are directly given, it is called Passive immunity
Solution: This statement is WRONG. Active immunity is slow and takes time to give its full response, not quick. The other three are correct: antibodies passed from mother to foetus (or ready-made antibodies given directly) are passive immunity, and antibodies made by the host after antigen exposure are active immunity.
NEET 2024
Assertion A: Breast-feeding during the initial period of infant growth is recommended by doctors for a healthy baby. Reason R: Colostrum contains several antibodies absolutely essential to develop resistance for the new-born baby.
A · Both A and R are correct, but R is NOT the correct explanation of A
B · A is correct but R is not correct
C · A is not correct but R is correct
D · Both A and R are correct, and R is the correct explanation of A ✓
Solution: Assertion A is correct: doctors recommend early breast-feeding for a healthy baby. Reason R is correct: colostrum has abundant antibodies (IgA) that give the newborn resistance (passive immunity) before its own immune system matures. R is exactly why breast-feeding is recommended, so R correctly explains A.
Solved Human Health and Diseases NEET PYQs
Try the real previous-year questions from this chapter — each with the answer and a full solution.
IgA. It is the antibody abundant in the yellowish first milk that protects the newborn's gut.
Is milk given from mother to baby active or passive immunity?
Passive immunity. The baby gets ready-made antibodies (IgA) and does not make them itself, so there is no immune memory.
What is colostrum in one line for NEET?
Colostrum is the yellowish fluid secreted in the first days of lactation, rich in IgA antibodies, giving the newborn passive immunity.
Why not choose macrophages in the 2019 PYQ?
Because the question asks what imparts immunity — that is the antibody IgA. Macrophages, monocytes and NK cells are innate-immunity cells, not the answer.
Which antibody crosses the placenta instead of coming through milk?
IgG crosses the placenta before birth. IgA comes after birth through colostrum. Both give passive immunity but at different stages.
