FITC Anti-Legionella pneumophila antibody (ab20818)

Thank you for contacting us and for presenting your questions so clearly! To amplify the the signal from the FITC-conjugated anti-Legionella antibody, your idea of using an Alexa Fluor 488-conjugated anti-FITC is a good one. We unfortunately do not have Alexa Fluor conjugates but these dyes have a good reputation for strong, stable signal. Another option is to follow the primary antibody with a biotinylated anti-rabbit IgG such as ab6720, and then a streptavidin or avidin fluorochrome conjugate. Again, we do not have these streptavidin/avidin/fluorochrome conjugates but they are available from other companies. The anti-rabbit IgG secondary will bind ab20818 even though it has FITC conjugated to it: https://www.abcam.com/Goat-Rabbit-IgG-HL-Biotin-ab6720.html We do have a phycoerythrin-conjugated anti-FITC, ab25539: https://www.abcam.com/PE-FITC-antibody-ab25539.html We do not have another fluorochrome-conjugated anti-Legionella antibody but we do have a biotin conjugate, ab20527: https://www.abcam.com/Biotin-Legionella-pneumophila-antibody-ab20527.html This can be used with the streptavidin/avidin conjugates I mentioned above. An antibody appropriate for labelling should have no other proteins in the buffer it is delivered in, as these will compete with the antibody for the label. Another consideration is that, since you already have a rabbit polyclonal antibody that will recognize potentially several epitopes, and it is not clear what exactly on the bacterium it binds, another polyclonal antibody applied before this one may interfere with it, and vice versa. Your best strategy, aside from using two monoclonal antibodies, is to apply a monoclonal antibody first, such as ab20444: https://www.abcam.com/Legionella-pneumophila-antibody-266-ab20444.html This will bind a single epitope on a single protein. It may interfere somewhat with the rabbit antibody that follows it but chances are the rabbit antibody will recognize other proteins on the bacterium in addition to, or other than, what the monoclonal binds. Antibody ab20444 is also suitable for conjugation: it is purified and there are no other proteins in the solution. The order in which these antibodies are used is important. Do not apply the rabbit polyclonal ab20818 before the mouse monoclonal ab20444; the rabbit may very well hinder the mouse antibody. I hope this helps. Please let us know if you have any other questions or concerns.