The humoral response involves antibodies made by plasma cells. An antigen binding to the specific binding site of that antibody is one stimulus to the cell to divide. Binding of antibody to a foreign object, like a bacterium, aids in targeting it for phagocytosis by macrophages. The humoral response, more than the cellular response, is responsible for removing virus-infected cells. A B-cell, stimulated to further differentiate, divides to generate a clone of plasma cells and some memory cells.
Plasma cells secrete large amounts of highly specific antibody.
Since simple combining of the antibody gene segments does not generate the billions of different antibodies that can be produced, other processes also occur. In rearranging the genes, extra nucleotides are inserted at the J-regions. Recombination of the genes is not precise. Binding of the specific antigen stimulates a B-cell to amplify the immunoglobulin genes so there are many more copies of the immunoglobulin genes. Damaged tissue releases histamine that attracts white blood cells.