Which of the following statements are fundamental to the clonal selection theory of how the adaptive immune system functions?
I. Each lymphocyte has a unique membrane receptor that recognises one antigen.
II. When the lymphocyte binds an antigen, it is activated and begins dividing to form many identical copies of itself.
III. Cloned lymphocytes have slight differences and are selected by the spleen for removal if they do not bind an antigen.
IV. Cloned cells descend from an activated lymphocyte and persist even after the pathogen is eliminated.
A) only I and III
B) only II and IV
C) only I, II, and IV
D) only II, III, and IV

Question

Quizplus · Accepted Answer

The clonal selection theory proposes that each lymphocyte has a unique membrane receptor that recognises one specific antigen (statement I). When this receptor binds to its antigen, the lymphocyte is activated and begins dividing to form many identical copies of itself (statement II). These clones may have slight differences, but they are selected by the spleen or lymph nodes for survival if they bind to the presenting antigen, and elimination otherwise (statement III is incorrect). Finally, the cloned cells descend from the activated lymphocyte and persist even after the pathogen is eliminated, thus providing long-lasting immunity (statement IV). Therefore, only statements I, II, and IV are fundamental to the clonal selection theory, making choice C the best answer.

Which of the Following Statements Are Fundamental to the Clonal