Antibodies produced by a single clone of plasma cells are called which of the following?

• A. Reagin
• B. Cold agglutinins
• C. Heterophile antibodies
• D. Monoclonal antibodies

Answer: (D)

Monoclonal antibodies are produced by a single clone of plasma cells, so they are identical in structure and recognize the same specific epitope. This uniformity comes from all antibody-secreting cells deriving from one parent B cell, making the population highly specific and consistent for diagnostic or therapeutic use. In contrast, many antibodies generated during a typical immune response come from multiple B-cell clones, producing a polyclonal mixture that targets several epitopes with varying affinities.

The other terms describe antibodies that are not from a single clone: reagin refers to nonspecific antibodies involved in certain serologic tests, cold agglutinins are usually IgM antibodies that can be polyclonal and react at cold temperatures, and heterophile antibodies are cross-reactive antibodies not derived from a single clone.