Every normal baby is born with an enormous number of different clones of B cells. Populations of these cells are found in the bone marrow, lymph nodes, and spleen. All the cells of each clone are already committed to synthesizing a specific antibody. The sequence of amino acids in the variable regions of a specific antibody is different from the sequence in all the countless clones of B cells in the baby’s body. This enormous variability may be due to the way the genes encode for the antibodies. In a way, the system acts like a genetic lottery, producing millions of unique genes by combining different gene segments to produce the unique polypeptides.