Positive Control vs Negative Control

Positive Control vs Negative Control

T cell activation is a crucial process in the immune response, playing a pivotal role in how the body responds to pathogens and maintains immune homeostasis. This intricate process involves several key stages and molecules, each contributing to the effective functioning of T cells in the immune system.

Understanding the Basics of T Cell Activation

Direct conjugation involves the direct covalent attachment of the molecule to the antibody. This method is straightforward but requires careful control of reaction conditions to ensure specificity and retain antibody functionality.

Indirect Conjugation

Indirect conjugation uses a two-step process. Initially, a reactive group is attached to the antibody, which subsequently reacts with the molecule to be conjugated. This method offers greater control and can improve the stability of the conjugate.

Site Specific Conjugation

Advancements in genetic engineering have enabled site-specific conjugation. This technique involves modifying the genetic sequence of the antibody to include specific sites for conjugation, ensuring uniformity and consistency in the conjugates

Applications in Research and Diagnostics

Targeted Drug Delivery

In therapeutics, antibody-drug conjugates (ADCs) are used for targeted drug delivery, especially in cancer treatment. ADCs deliver cytotoxic drugs directly to cancer cells, minimizing systemic toxicity.

Diagnostic Assays

In diagnostics, conjugated antibodies are used in various assays, including enzyme-linked immunosorbent assay (ELISA) and immunohistochemistry (IHC). Fluorescent or enzyme-labeled antibodies provide precise detection and quantification of specific antigens.

Research and Development

In research, antibody conjugates are crucial in studying cell biology, protein interactions, and disease mechanisms. They are used in flow cytometry, Western blotting, and immunoprecipitation assays.

Antibody Conjugate Wavelength Application

495 nm / 519 nm

Used in flow cytometry, immunofluorescence microscopy, and ELISA.

565 nm / 578 nm

Common in flow cytometry and immunofluorescent staining due to bright fluorescence.

650 nm / 660 nm

Suitable for flow cytometry in multicolor panels.


Used in ELISA, Western blotting and IHC oftern with streptavidin.


Employed in ELISA, Western blotting, and IHC for enzymatic signal detection.

Cy3-Conjugated Antibodies

550nm / 570 nm

Utilized in fluorescence microscopy and flow cytometry for its bright, stable fluorescence.

Cy5-Conjugated Antibodies

649 nm / 670 nm

Preferred for fluorescence microscopy and multicolor flow cytometry, especially in NIR spectrum.

482 nm / 675 nm

Used in flow cytometry, compatible with multiple lasers and suitable for multicolor staining.

DyLight Fluor-Conjugated Antibodies


A range of DyLight Fluors are used for high-intensity fluorescence in microscopy and flow cytometry.

Alexa Fluor-Conjugated Antibodies


Alexa Fluor dyes cover a wide range of wavelengths and are used for their brightness and photostability in various applications.

Challenges and Considerations

Maintaining Antibody Integrity

A key challenge in antibody conjugation is maintaining the integrity and specificity of the antibody post-conjugation. Over-conjugation or improper conjugation can hinder the antibody's binding ability.

Optimization of Conjugation Ratio

Determining the optimal ratio of the molecule to the antibody is crucial for functionality and efficacy, particularly in therapeutic applications.

Scale-Up and Reproducibility

Scaling up conjugation processes while ensuring consistency and reproducibility is critical, especially for clinical and diagnostic applications.

In conclusion, antibody conjugation is a versatile and essential technique in biomedicine, with applications ranging from cancer therapy to diagnostics. Ongoing advancements in conjugation methods continue to expand its potential, promising more effective and targeted biomedical interventions.

Additional Resources

24th Aug 2023 Niamh Murphy MSc

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