Read the passage and answer the question given below.
When a host is exposed to antigens, which may be in the form of living or dead microbes or other proteins, antibodies are produced in the host body. This type of immunity is called active immunity. Active immunity is slow and takes time to give its full effective response. Injecting the microbes deliberately during immunisation or infectious organisms gaining access into body during natural infection induce active immunity. When antibodies are directly given to protect the body against foreign agents, it is called passive immunity.
Colostrum secreted by mother during initial stage of lactation provides passive immunity as it is rich in.
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → IgA antibodies
The newborn receives ready-made antibodies from the mother's milk instead of making its own, so this is passive immunity.
Option (1) Placental lactogen — Incorrect. Human placental lactogen is a hormone of the placenta during pregnancy; it is not in colostrum and gives no immunity.
Option (2) Prolactin — Incorrect. Prolactin is the pituitary hormone that starts milk production; it does not protect against infection.
Option (3) Antigen — Incorrect. Antigens are the foreign substances that cause antibody production; giving antigens would produce active immunity.
Option (4) IgA antibodies — Correct. The yellowish fluid colostrum, secreted in the initial days of lactation, has abundant IgA antibodies. They protect the infant, giving passive immunity.
Note: The passage is taken from NCERT. NTA has put lines of the NCERT text together to make it. Most CUET (UG) questions come straight from NCERT, so study the book line by line, including figures and their titles.
NCERT Extract:
Active and 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.”