FITC-conjugated anti-mouse primary antibodies are directly labeled immunoreagents that combine a mouse antigen-specific immunoglobulin with the green-emitting fluorescein isothiocyanate (FITC) fluorophore. Unlike FITC-conjugated secondary antibodies, which recognize mouse immunoglobulins, FITC-conjugated primary antibodies bind their target mouse antigen directly, enabling single-step staining without the need for a secondary reagent.

FITC is the form of fluorescein used for conjugation to antibodies and purified proteins. It exhibits an excitation maximum of approximately 492–495 nm and an emission maximum of approximately 520–528 nm, producing bright green fluorescence. FITC 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, FITC remains a widely used fluorophore due to its long history and broad compatibility with existing instrumentation. The major disadvantage of fluorescein is its rapid photobleaching, which can be mitigated by the use of an anti-fading agent in the mounting medium. Alexa Fluor 488 is a brighter and more photostable alternative for many applications.

Applications

Flow Cytometry

FITC-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 of FITC-conjugated primary antibodies is typically 0.1–1.0 µg per million cells in 100 µL volume. The recommended concentration is 0.1–1 µg per 10⁶ cells. Each investigator should titrate the reagent for optimal performance for each application.

Immunofluorescence and Immunohistochemistry

FITC-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 of FITC is well separated from red and far-red fluorophores, facilitating dual- and triple-labeling experiments.

ELISA

FITC-conjugated anti-mouse IgG1 (clone RMG1-1) may be used as a primary or secondary reagent for ELISA or immunofluorescent analysis.