What kind of immunity is provided to the infant by colostrum?

The correct answer is Option (2) → Passive immunity

Option (1) Active immunity — Incorrect. Active immunity develops when the body meets antigens and makes its own antibodies; it is slow to start. The infant’s body has not made the IgA in colostrum.

Option (2) Passive immunity — Correct. Colostrum carries ready-made IgA antibodies from mother to baby. Protection from antibodies made by another body is passive immunity; the baby’s own body did not make them.

Option (3) Auto immunity and passive immunity — Incorrect. Auto-immunity is not a kind of protection. It is a disorder in which the body attacks self-cells, as in rheumatoid arthritis. Colostrum gives only passive immunity.

Option (4) Active as well as Passive immunity — Incorrect. Colostrum supplies ready-made antibodies only. Nothing in it makes the infant’s own body produce antibodies, so no active immunity is given.

NCERT Extract:
Active and Passive Immunity – “When ready-made antibodies are directly given to protect the body against foreign agents, it is called passive immunity. … The yellowish fluid colostrum secreted by mother during the initial days of lactation has abundant antibodies (IgA) to protect the infant. The foetus also receives some antibodies from their mother, through the placenta during pregnancy. These are some examples of passive immunity.”