Secondary antibodies are affinity-purified antibodies which will work with target-specific primary antibody in the detection, sorting or purification of its specified target. Secondary antibodies offer increased versatility enabling users to use many detection systems (e.g. HRP, AP, fluorescence). They can also provide greater sensitivity through signal amplification as multiple secondary antibodies . Most commonly, secondary antibodies are generated by immunizing the host animal (different from host species of primary antibody) with a pooled population of normal immunoglobulins from the host species of primary antibody and can be further purified and modified (i.e. antibody fragmentation, label conjugation, etc.) to ensure well-characterized specificity to corresponding normal immunoglobulins.