What is meant by clones of B-cells? I was reading Cellular and Molecular Immunology By Abul K. Abbas, Andrew H. H. Lichtman, Shiv Pillai and stumbled upon the following excerpt $-$ > In every individual there are millions of different clones of B-cells,each producing antibody molecules with the same antigen binding site and different in this site from the antibodies produced by other clones. What are these clones of B-cells, one producing monoclonal antibodies and the other polyclonal antibodies?

When you read further you'll get it. Basically, when the antibody expressed on a B-cell recognizes an antigen, then the B-cell divides and expands its population to produce more antibodies (through plasma cells). This process is called clonal expansion.