Which of the following cells produce antibodies?

The correct answer is Option (4) → B-lymphocytes

Antibodies are proteins that bind to a particular antigen of a pathogen. Each antibody has four peptide chains, two light and two heavy (H₂L₂).

Option (1) Monocytes — Incorrect. Monocytes are phagocytes; they engulf and destroy microbes as part of innate immunity.

Option (2) PMNL neutrophils — Incorrect. Polymorpho-nuclear leukocytes (PMNL), the neutrophils, are also phagocytes of the cellular barrier of innate immunity.

Option (3) T-lymphocytes — Incorrect. T-cells do not secrete antibodies, but they help B-cells to produce them, and they carry out cell-mediated immunity.

Option (4) B-lymphocytes — Correct. B-cells produce antibodies in response to pathogens, which is the humoral immune response.

NCERT Extract:
Acquired Immunity – “… The primary and secondary immune responses are carried out with the help of two special types of lymphocytes present in our blood, i.e., B-lymphocytes and T-lymphocytes. The B-lymphocytes produce an army of proteins in response to pathogens into our blood to fight with them. These proteins are called antibodies.”