PE-conjugated anti-horse primary antibodies are bright orange-fluorescent immunoreagents optimized for high-sensitivity detection in flow cytometric applications. Produced by immunizing hosts such as goat, rabbit, or mouse with purified horse immunoglobulins, the antibodies are affinity-purified and covalently conjugated to R-phycoerythrin (R-PE), a 240 kDa phycobiliprotein derived from red algae (Rhodophyta). R-PE exhibits one of the highest extinction coefficients (≈ 1.96 × 10⁶ M⁻¹cm⁻¹) and quantum yields (≈ 0.84) among available fluorophores, making it approximately 10–20 times brighter than small-molecule dyes such as FITC and Alexa Fluor^® 488. Excitation maxima at 488 nm (principal) and 565 nm (secondary), with emission at 578 nm, enable compatibility with standard 488 nm argon-ion and 561 nm solid-state lasers. The large Stokes shift minimizes light-scatter interference, while the high brightness facilitates detection of equine antigens expressed at very low copy numbers on cell surfaces. Available specificities include anti-IgG (H+L), recognizing heavy and light chains; anti-IgG (Fc), targeting the constant region; anti-IgG1; anti-IgG2; anti-IgA; and anti-IgM isotype-specific reagents. Extensive cross-adsorption against immunoglobulins from mouse, rat, rabbit, bovine, sheep, and human helps minimize nonspecific binding in cross-reactive samples.

Applications

PE conjugates are extensively employed in flow cytometry and fluorescence-activated cell sorting (FACS) for immunophenotyping equine leukocytes, detecting surface markers including CD4, CD8, CD11a/CD18 (LFA-1), CD14, CD21, and MHC class II (equine leukocyte antigen). The exceptional brightness enables detection of antigens expressed at very low copy numbers, as low as 500 molecules per cell, making PE a preferred fluorophore for low-abundance targets in multicolor panels. In multiplex bead-based assays, PE conjugates serve as reporter fluorophores for cytokine and biomarker quantification using Luminex^® xMAP^® and similar technologies. These conjugates are also applicable in immunofluorescence microscopy, where the bright orange emission facilitates antigen localization in tissue sections and cultured cells. In cell proliferation and apoptosis assays, PE conjugates enable detection of intracellular cytokines such as IFN-γ, IL-4, and IL-10 following stimulation. They are compatible with fixative solutions such as paraformaldehyde but should be protected from light and should not be frozen, as freezing can cause aggregation and loss of fluorescence. Typical working dilutions range from 1:50 to 1:500 for flow cytometry, 1:100 to 1:1,000 for immunofluorescence, and 1:1,000 to 1:5,000 for ELISA. These reagents are intended for research use only and are not for diagnostic procedures.