Fluorescein-conjugated anti-mouse primary antibodies are directly labeled immunoreagents that combine a mouse antigen-specific immunoglobulin with the green-emitting fluorescein fluorophore. Unlike fluorescein-conjugated secondary antibodies, which recognize mouse immunoglobulins, fluorescein-conjugated primary antibodies bind their target mouse antigen directly, enabling single-step staining without the need for a secondary reagent.
Fluorescein is a xanthene-based fluorescent dye. While the isothiocyanate derivative (FITC) is most commonly used for conjugation, the resulting antibody conjugate is frequently referred to simply as "fluorescein-conjugated." The fluorophore exhibits an excitation maximum of approximately 492–495 nm and an emission maximum of approximately 520–528 nm, producing bright green fluorescence. It is efficiently excited by the 488 nm blue laser standard on most flow cytometers and can be detected using a 530/30 nm or 525/40 nm bandpass filter. Although less bright than other green-fluorescing dyes, fluorescein remains widely used due to its long history and broad compatibility with existing instrumentation. The major disadvantage is its rapid photobleaching, which can be mitigated by using an anti-fading mounting medium.
Applications
Flow Cytometry
Fluorescein-conjugated anti-mouse primary antibodies are validated primarily for flow cytometry, enabling direct immunophenotyping of mouse leukocyte subsets. Each lot is quality control tested by immunofluorescent staining with flow cytometric analysis.
For flow cytometric staining, the suggested use is typically 0.1–1.0 µg per million cells in 100 µL volume. Each investigator should titrate the reagent for optimal performance.
Immunofluorescence and Immunohistochemistry
Fluorescein-conjugated anti-mouse primary antibodies are used for immunofluorescence microscopy, enabling direct visualization of mouse antigens in cultured cells and tissue sections. The green emission is well separated from red and far-red fluorophores, facilitating dual- and triple-labeling experiments.
ELISA
Fluorescein-conjugated anti-mouse IgG1 may be used as a primary or secondary reagent for ELISA or immunofluorescent analysis.