outline the principles of using monoclonal antibodies in the diagnosis of disease and in the treatment of disease

Antibodies and \cdot accination

Monoclonal Antibodies (mAbs)

Monoclonal antibodies are identical immunoglobulin molecules produced by a single clone of B‑cells. They recognise a single, defined epitope on an antigen with high specificity and affinity. The hybridoma technique (fusion of a specific B‑cell with a myeloma cell) is the most common method for generating mAbs.

Principles of Using Monoclonal Antibodies in Diagnosis

Diagnostic applications exploit the ability of mAbs to bind selectively to disease‑associated antigens. The key principles are:

• Specificity: Each mAb recognises one epitope, reducing cross‑reactivity and false‑positive results.
• Sensitivity: High‑affinity binding (often expressed as a low dissociation constant \$K_d\$) allows detection of minute quantities of antigen.
• Reproducibility: Unlimited production of identical antibodies ensures consistent test performance.
• Versatility: mAbs can be labelled with enzymes, fluorophores, or radioisotopes for various assay formats (ELISA, immunofluorescence, Western blot, flow cytometry).

Common Diagnostic Formats

1. Enzyme‑Linked Immunosorbent Assay (ELISA): A capture mAb is immobilised on a plate; patient sample is added, and bound antigen is detected with a second enzyme‑conjugated mAb.
2. Rapid Lateral Flow Tests: Strips contain a coloured mAb that migrates with the sample; binding to target antigen produces a visible line.
3. Immunohistochemistry (IHC): Tissue sections are probed with a labelled mAb to visualise the presence and localisation of disease markers.
4. Flow Cytometry: Fluorescent mAbs label cell‑surface antigens, enabling quantitative analysis of cell populations (e.g., CD4⁺ T‑cells in HI \cdot monitoring).

Principles of Using Monoclonal Antibodies in Treatment

Therapeutic mAbs act by targeting specific molecules involved in disease pathology. Their mechanisms include:

• Neutralisation: Binding to a pathogen or toxin blocks its interaction with host cells (e.g., anti‑rabies mAbs).
• Receptor Blockade: Preventing ligand binding to cell‑surface receptors (e.g., anti‑TNF‑α mAbs in rheumatoid arthritis).
• Induction of Cytotoxicity: Fc region engages immune effector functions such as complement‑dependent cytotoxicity (CDC) or antibody‑dependent cellular cytotoxicity (ADCC).
• Delivery of Cytotoxic Agents: Conjugating mAbs to drugs, toxins, or radioisotopes directs these agents specifically to diseased cells (antibody‑drug conjugates).

Key Considerations for Therapeutic Use

1. Humanisation: Reducing immunogenicity by grafting murine complementarity‑determining regions onto a human IgG framework.
2. Pharmacokinetics: Optimising half‑life through Fc engineering or PEGylation.
3. Safety: Monitoring for infusion reactions, cytokine release syndrome, and off‑target effects.
4. Resistance: Tumour cells may down‑regulate the target antigen; combination therapies can mitigate this.

Examples of Diagnostic and Therapeutic Monoclonal Antibodies

Summary

Monoclonal antibodies provide a powerful tool for both the precise detection of disease markers and the targeted treatment of a wide range of conditions. Their high specificity, reproducibility, and adaptability to various assay formats make them indispensable in modern biomedical practice. Understanding the underlying principles of their design, production, and mechanism of action is essential for effective use in clinical diagnostics and therapeutics.