Q. 32 Which one of the following properties of the myeloma cells is used in the hybridoma technology to
generate monoclonal antibody?
(A) lack of thymidylate synthase
(B) over-expression of hypoxanthine-guanine phosphoribosyl transferase
(C) over-expression of inosine 5′-monophosphate cyclohydrolase
(D) lack of hypoxanthine-guanine phosphoribosyl transferase
Hybridoma technology revolutionized monoclonal antibody production by fusing B cells with myeloma cells. The key property exploited in myeloma cells is their lack of hypoxanthine-guanine phosphoribosyl transferase (HGPRT), enabling selective hybridoma growth in HAT medium.
Correct Answer
Option (D) lack of hypoxanthine-guanine phosphoribosyl transferase is correct. Myeloma cells deficient in HGPRT cannot survive in HAT (hypoxanthine-aminopterin-thymidine) medium, as aminopterin blocks de novo nucleotide synthesis, and they lack the salvage pathway enzyme HGPRT to utilize hypoxanthine. Fused hybridomas inherit functional HGPRT from B cells, allowing selective proliferation for monoclonal antibody production.
Option Explanations
-
(A) Lack of thymidylate synthase: Incorrect. Thymidylate synthase deficiency relates to thymidine salvage but is not the primary selection marker in hybridoma technology; HAT selection targets HGPRT.
-
(B) Over-expression of hypoxanthine-guanine phosphoribosyl transferase: Incorrect. Over-expression would enable myeloma survival in HAT medium, defeating selection; they must lack HGPRT.
-
(C) Over-expression of inosine 5′-monophosphate cyclohydrolase: Incorrect. This enzyme functions in de novo purine synthesis, unrelated to HAT salvage pathway selection relying on HGPRT absence.
-
(D) Lack of hypoxanthine-guanine phosphoribosyl transferase: Correct, as explained above.
Hybridoma Process Overview
Immunize mice with antigen to activate B cells, then fuse spleen B cells with HGPRT-deficient myeloma cells using PEG. Culture in HAT medium kills unfused myeloma (no HGPRT) and unfused B cells (short-lived), isolating hybridomas that secrete specific monoclonal antibodies indefinitely.
