Question

Explain "clonal expansion" of lymphocytes and how it contributes to the features of adaptive immunity, such as specificity, elimination of pathogens and memory.

Answer 1

Clonal lymphocyte expansion is a hallmark of adaptive vertebrate immunity, where a small number of precursor cells that recognize a particular antigen proliferate into extended clones, differentiate, and develop different effector and memory phenotypes that facilitate successful immune responses.

Lymphocytes are responsible for the remarkable specificity of the adaptive immune response. They exist in large amounts in the blood and lymph, a colorless fluid in lymphatic vessels that bind the lymph nodes in the body to each other, and the bloodstream and lymphoid organs such as thymus, lymph nodes, spleen, and appendix.

The adaptive immune system consists of millions of lymphocyte clones, with cells in each clone sharing a common cell-surface receptor that allows them to bind a particular antigen. Effector B cells secrete antibodies that can function over long distances to help remove extracellular pathogens and their toxins.