Primary Antibodies for Multiplex IHC (mIHC)

Conjugated primary antibodies for streamlined mIF and mIHC workflows

Fluorescence-based immunohistochemistry is a powerful method for detecting multiple protein targets within a single tissue section with sensitivity, specificity, and spatial context. Invitrogen conjugated primary antibodies for mIHC are labeled with Alexa Fluor and Alexa Fluor Plus dyes and are selected for strong fluorescence performance in tissue imaging workflows.

These ready-to-use conjugates are tested for target specificity using human formalin-fixed, paraffin-embedded (FFPE) tissue. The dye menu is designed to support 9-plex tissue labeling, with one channel reserved for DAPI, in a single round of staining. These antibodies help simplify multiplex IHC and improve workflow consistency, conserve samples, and generate high-quality multiplex imaging data.

Key benefits of directly conjugated primary antibodies for mIHC include:

One-step direct staining with no secondary antibody required.
Reduced assay complexity and lower hands-on effort.
Conjugated to bright, photostable fluorophores for tissue imaging.
Broad spectral diversity for multiplex panel development.
Compatibility with conventional and spectral imaging systems.
Fewer cyclic labeling rounds for high-plex tissue analysis.

Fluorophore options for up to 9-plex mIHC

Conjugated primary antibodies for mIHC are available across a broad fluorophore menu spanning DAPI, Alexa Fluor 420, Alexa Fluor Plus 488, Alexa Fluor 514, Alexa Fluor Plus 555, Alexa Fluor Plus 594, Alexa Fluor Plus 647, Alexa Fluor 700, and Alexa Fluor Plus 750. This spectral range, from UV to near-infrared (NIR), helps researchers select fluorophores based on target abundance, imaging instrument, detector channels, and multiplex panel design.

The broad dye menu supports efficient detection of multiple markers in one sample, facilitating panel design and spatial interrogation of biological features including immune profiling, tumor proliferation, stromal organization, and immune cell activation status.

Figure 1. 9-plex mIHC staining on normal human FFPE colon tissue. This 9-color multiplex IHC panel enables simultaneous spatial mapping of epithelial, immune, proliferative, and signaling biomarkers in normal human FFPE colon tissue, providing a multidimensional view of tissue organization and cellular interactions within the native microenvironment.

The section was co-stained with beta Catenin Monoclonal Antibody (15B8), Alexa Fluor 420 (teal), CD68 Monoclonal Antibody (KP1), Alexa Fluor Plus 488 (Cat. No. 752-0688-82, green), CD3e Recombinant Rabbit Monoclonal Antibody (RM344) (Cat. No. MA562126) labeled with ReadyLabel 20 µg Antibody Labeling Kit Alexa Fluor 514 (Cat. No. R10720, yellow), CD8 alpha Monoclonal Antibody (C8/144B), Alexa Fluor Plus 555 (Cat. No. 754-0085-82, orange), p53 Monoclonal Antibody (DO-7), Alexa Fluor Plus 594 (Cat. No. 755-8002-94, red), PD-1 (CD279) Recombinant Rabbit Monoclonal Antibody (RM309), Alexa Fluor Plus 647 (Cat. No. 756-8003-94, magenta), Pan Cytokeratin Monoclonal Antibody (AE1/AE3), Alexa Fluor 700 (Cat. No. 56-9003-82, purple), and Ki-67 Monoclonal Antibody (SolA15), Alexa Fluor Plus 750 (Cat. No. 757-5698-82, white). Nuclei were stained with DAPI (Cat. No. D1306, blue) and the section was mounted using ProLong Glass Antifade Mountant (Cat. No. P36984). The image was captured and unmixed on Invitrogen EVOS S1000 Spatial Imaging System (Cat. No. AMFS1000) at 20X magnification.

Figure 2. 6-plex mIHC staining on human FFPE breast adenocarcinoma tissue. High-resolution spatial characterization of the breast adenocarcinoma tumor microenvironment using 6-color multiplex panel for simultaneous visualization of tumor architecture, EGFR expression, immune cell infiltration, and stromal organization within a single FFPE tissue section.

The section was co-stained with EGFR Recombinant Rabbit Monoclonal Antibody (30H45L48), Alexa Fluor Plus 750 (Cat. No. 757-8804-94, red), CD3e Recombinant Rabbit Monoclonal Antibody (RM344) (Cat. No. MA562126) labeled with ReadyLabel 20 µg Antibody Labeling Alexa Fluor Plus 647 (Cat. No. R10710, magenta), CD8 alpha Monoclonal Antibody (C8/144B), Alexa Fluor Plus 594 (Cat. No. 755-0085-82, green), Cytokeratin Pan Type I/II Monoclonal Antibody (AE1/AE3), Alexa Fluor Plus 555 (Cat. No. 754-9003-82, cyan), CD68 Monoclonal Antibody (KP1), Alexa Fluor Plus 488 (Cat. No. 752-0688-82, yellow), and Alpha-Smooth Muscle Actin Monoclonal Antibody (1A4), Alexa Fluor Plus 420 (Cat. No. 758-9760-82, white). Nuclei were stained with DAPI (Cat. No. D1306, blue) and the section was mounted using ProLong Glass Antifade Mountant (Cat. No. P36984). The image was captured and unmixed on Invitrogen EVOS S1000 Spatial Imaging System (Cat. No. AMFS1000) at 20X magnification.

Figure 3. 6-plex mIHC staining on human FFPE kidney tissue. This 6-color multiplex IHC panel captures the spatial organization of human FFPE kidney tissue by simultaneously visualizing epithelial, stromal, vascular, and extracellular matrix compartments. The panel provides clear delineation of renal tissue architecture, enabling detailed assessment of cellular organization and tissue integrity within a single section.

The section was co-stained with Vimentin Monoclonal Antibody (V9), Alexa Fluor 420 (Cat. No. 758-9897-82, green), Alpha-Smooth Muscle Actin Monoclonal Antibody (1A4), Alexa Fluor Plus 488 (Cat. No. 752-9760-94, white), Pan Cytokeratin Monoclonal Antibody (AE1/AE3), Alexa Fluor 514 (Cat. No. 753-9003-82, yellow), E-cadherin Monoclonal Antibody (4A2C7), Alexa Fluor Plus 555 (magenta), CD31 Recombinant Rabbit Monoclonal Antibody (RM247) (Cat. No. MA5-33063) labeled with ReadyLabel 20 µg Antibody Labeling Kit, Alexa Fluor 700 (Cat. No. R10723, red), and Collagen IV Monoclonal Antibody (1042), Alexa Fluor Plus 750 (Cat. No. 757-9871-82, cyan). Nuclei were stained with DAPI (Cat. No. D1306, blue) and the section was mounted using ProLong Glass Antifade Mountant (Cat. No. P36984). The image was captured and unmixed on Invitrogen EVOS S1000 Spatial Imaging System (Cat. No. AMFS1000) at 20X magnification.

Multiplex IHC panel design considerations

Successful multiplex IHC panel design depends on selecting antibodies and fluorophores that match both target biology and instrument capabilities. Pairing target abundance with appropriate fluorophore brightness can improve signal detection, reduce background, and minimize spectral spillover.

When designing a multiplex IHC panel:

Select IHC-verified antibodies with expected staining patterns in the tissue type of interest.
Identify the imaging instrument and available detector channels before selecting dyes.
Use bright fluorophores for low-abundance targets or difficult-to-resolve targets.
Use moderate-to-lower brightness fluorophores for highly abundant targets.
Reserve the brightest fluorophores for unknown-expression markers or challenging targets.
Minimize spectral overlap and spillover to reduce cross-talk in conventional imaging.
Prioritize photostable fluorophores for extended imaging workflows.

Figure 4. Recommended fluorophore selection based on antigen abundance or marker intensity in multiplex IHC. This schematic illustrates general guidance for matching fluorophore brightness to target abundance to support balanced signal detection in multicolor tissue imaging. Brighter fluorophores are recommended for low-abundance or low-intensity targets (+), while moderately bright fluorophores are suited for intermediate-abundance targets (++), and dimmer fluorophores are better matched to high-abundance or high-intensity targets (+++), where overly bright dyes may increase the risk of signal saturation.

Antibody selection and verification for IHC

Choose antibodies for multiplex IHC based on verified target specificity, application performance, tissue type, and compatibility with the staining protocol. For multiplexing, antibodies should work under similar staining conditions to support reliable panel performance.

Antibody verification for IHC is strengthened by advanced verification methods that include specificity testing and testing in complementary applications such as western blotting (WB) and immunocytochemistry (ICC). These data help support reliable and reproducible staining results.

Common specificity verification methods include:

Knockout
genetic silencing of a protein using CRISPR-Cas9 technology

Knockdown
using RNA interference-based reduction of the target of interest

Cell treatment
detection of downstream expression or localization changes after treatment

Relative expression
use of naturally occurring variable expression to confirm specificity

Ki-67 antibody verification data

Thermo Fisher Scientific verification data for Ki-67 antibody clone SolA15 demonstrate suitability for immunohistochemistry. In HeLa cells, Ki-67 upregulation after 36 hours of serum starvation followed by serum release supports specificity through cell treatment-based verification. Specificity was further confirmed by knockout validation, where loss of Ki-67 signal in knockout cells compared with wild-type and control cells demonstrated precise target detection. Together, these data support the antibody’s target specificity, IHC verification, and value for reliable antibody selection in multiplex IHC and FFPE tissue staining workflows.

Figure 5. Immunofluorescence analysis of Ki-67 was performed on HeLa cells serum starved for 36 hours with or without serum release for 6 Hrs. The cells were labeled with Ki-67 Monoclonal Antibody (SolA15), eBioscience (Cat. No. 14-5698-82) and detected with Goat anti-Rat IgG (H+L) Cross-Adsorbed Secondary Antibody, Alexa Fluor 488 (Cat. No. A1-1006, green). F-actin was stained with Rhodamine Phalloidin (Cat. No. R415, red). Nuclei were stained with SlowFade Gold Antifade Mountant with DAPI (Cat. No. S36938, blue).

Figure 6. Antibody specificity was demonstrated by CRISPR-Cas9 mediated knockout of target protein. A loss of signal was observed for target protein in Ki-67 KO cell line compared to control cell line using Ki-67 Monoclonal Antibody (SolA15), eBioscience (Cat. No. 14-5698-82).

Figure 7. Immunohistochemical analysis of Ki-67 was performed using formalin-fixed paraffin-embedded human colon adenocarcinoma tissue sections probed with or without Ki-67 Monoclonal Antibody (SolA15), eBioscience (Cat. No. 14-5698-82) and detected using Goat anti-Rat IgG (H+L) Cross-Adsorbed Secondary Antibody, Alexa Fluor 488 (Cat. No. A-11006). Nuclei were stained with DAPI (Cat. No. D1306) and the sections were mounted using ProLong Glass Antifade Mountant (Cat. No. P36984). The images were captured on Invitrogen EVOS M7000 Imaging System (Cat. No. AMF7000) at 20X magnification.

Verifying conjugated primary antibodies for mIHC

For conjugated primary antibodies used in multiplex IHC, performance is compared with secondary-antibody labeling to help verify tissue staining quality, antibody specificity, and product selection. Researchers should also use positive and negative control tissues, confirm expected subcellular localization, evaluate tissue autofluorescence, and optimize signal-to-background ratio.

Figure 8. Immunohistochemical analysis of PD-1 was performed on FFPE human tonsil tissue. Tissues were probed with PD-1 (CD279) Recombinant Rabbit Monoclonal Antibody (RM309), Alexa Fluor Plus 647 (Cat. No. 756-8003-94) (left) or with PD-1 (CD279) Recombinant Rabbit Monoclonal Antibody (RM309) (Cat. No. MA5-27899) (right). Detection of the unconjugated primary antibody was performed using Goat anti-Rabbit IgG (H+L) Secondary Antibody, Alexa Fluor Plus 647 (Cat. No. A32733). The sections were stained with DAPI (Cat. No. 62247, 1 µg/mL) and mounted with ProLong Glass Antifade Mountant (Cat. No. P36984). Images were captured on Invitrogen EVOS M7000 Imaging System (Cat. No. AMF7000) at 20X magnification.

Need a conjugated antibody that is not available off the shelf?

Invitrogen antibody labeling kits allow researchers to conjugate an antibody of choice with fluorophores optimized for added flexibility in multiplex IHC panel design.

Explore antibody labeling kits

Need stronger signal detection in multiplex IHC?

For multiplex IHC, signal amplification reagents can enhance detection of low-abundance biomarkers by increasing signal intensity when expression is weak or difficult to resolve. This can improve confidence in target visualization while supporting high-quality tissue staining and multicolor imaging.

Aluora Spatial Amplification Reagents provide options signal amplification, flexible assay design, and enhanced detection in FFPE tissue samples.

Explore spatial amplification kits

FAQ

Conjugated primary antibodies are antibodies directly linked to a detectable label, such as a fluorescent dye or enzyme, allowing direct target detection without a labeled secondary antibody.

Direct detection uses a labeled primary antibody, while indirect detection uses an unlabeled primary antibody followed by a labeled secondary antibody. Direct detection can simplify multiplex IHC workflows and reduce cross-reactivity risk.

They support one-step tissue staining, reduce workflow complexity, and eliminate the need for a secondary antibody.

Choose fluorophores based on target abundance, instrument channels, spectral overlap, and photostability. Bright fluorophores are typically better for low-abundance targets, while moderate-to-lower brightness fluorophores may be better for highly abundant targets.

Antibodies are evaluated using specificity verification methods such as knockout, knockdown, cell treatment, and relative expression, together with application verification. For conjugated primary antibodies, performance may also be compared with secondary-antibody labeling.