B cells are a type of cells that produce antibodies. Each B cell produces a different type of antibody. For example, consider the following B cells: C1, C2, and C3, which produce antibodies A1, A2, and A3, respectively. We are dealing with 3 B cell clones, given that they produce 3 different types of antibodies.
Let's say that the B cell C1 happens to produce antibodies (A1) that are specific against the lipopolysaccharide (LPS) of a certain bacteria. When this bacteria enters the body, C1 will detect its presence and become activated. Two things happen when a B cell becomes activated: (1) differentiation, and (2) proliferation. Therefore, from the B cell clone C1 many more B cells will be produced through cell division, and all of these cells will produce antibodies A1 with the same affinity towards LPS. This would be a monoclonal antibody response, given that only antibodies from one B cell clone are produced.
If B cell C2 also produces antibodies (A2) with affinity for LPS, then upon bacterial infection C2 would become activated, proliferate, and differentiate. Given that antibodies (A1 and A2) from two different B cell clones (C1 and C2) are produced, this is a polyclonal antibody response.
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