Antibodies as Diagnostic Tools
One of the most widespread uses of antibodies is in diagnostic tests. Because an antibody will bind only its target antigen, it can serve as a very precise probe to detect the presence of that target in a sample.
Monoclonal antibodies (lab-produced identical antibodies) can be mass-produced against virtually any molecule of interest, enabling highly sensitive tests for diseases and health conditions. Today, hospitals, clinics, and even home pregnancy and disease test kits rely on antibody-based diagnostics. Some common antibody-based diagnostic techniques include:
ELISA (Enzyme-Linked Immunosorbent Assay)
A staple lab test that enables sensitive detection of hormones, pathogens, and biomarkers by capturing targets with specific antibodies. Modern “fourth‑ and fifth‑generation” combination ELISAs are the recommended first‑line screen for HIV, while similar platforms still confirm pregnancy via hCG detection. This method is highly sensitive and relatively quick.
Rapid diagnostic tests (lateral flow assays)
Portable, paper‑strip tests that use antibodies to give results within minutes. These include at‑home tests like the COVID‑19 antigen test or malaria kits, where antibodies on the strip bind target molecules in a drop of blood or swab sample and produce a visible line if positive. Most commercial kits detect as little as 100–1000 pg mL‑1 of antigen, depending on the label chemistry.
Western Blot
A laboratory method to detect specific proteins in a sample. After separating proteins by size on a gel, antibodies are applied to identify the protein of interest. Western blots were once the routine confirmation for HIV after an ELISA screen, but current CDC guidance now uses an HIV‑1/2 antibody differentiation immunoassay instead. The technique remains important for confirming Lyme disease, detecting protease‑resistant prion proteins, and validating protein expression in research and vaccine production.
Immunohistochemistry (IHC)
IHC uses antibodies to detect specific antigens in tissue sections and is a routine method for identifying disease markers under the microscope. In cancer care, IHC helps classify tumor types and guide therapy by revealing which proteins the tumor expresses. For example, pathologists use antibodies to test if a breast tumor overproduces the HER2 receptor or if a lung tumor expresses PD‑L1, results that predict whether therapies like trastuzumab or anti‑PD‑1 immunotherapy will be effective.
Therapeutic Applications of Antibodies
Direct Neutralization of Pathogens or Toxins
Monoclonal antibodies (mAbs) have become a major therapeutic class for cancers, autoimmune disorders, and infectious diseases. Many therapeutic antibodies neutralize harmful targets directly. For instance, antibodies against viral proteins can block a virus from infecting cells. An antibody binding the SARS‑CoV‑2 spike protein prevents the virus from entering cells, thereby neutralizing infection.
Similarly, toxin‑neutralizing antibodies can bind a toxin’s active site to inactivate it. This principle is used in antidotes for venom and in therapies like palivizumab, which is given prophylactically to prevent severe respiratory syncytial virus infection in at‑risk infants.
Immune Modulation in Autoimmune and Inflammatory Diseases
Therapeutic mAbs can modulate excessive immune signals. Many monoclonal antibodies are now approved for autoimmune conditions such as rheumatoid arthritis, psoriasis, and inflammatory bowel disease. These include antibodies like infliximab and adalimumab that bind tumor necrosis factor-alpha (TNF-α), a key inflammatory cytokine, to neutralize its effect, thereby reducing inflammation in joints and tissues. Likewise, tocilizumab, an anti-IL-6 receptor antibody, is used to calm cytokine-driven inflammation in rheumatoid arthritis and was repurposed to mitigate severe inflammatory responses in COVID-19.
Checkpoint Inhibition and Immune Activation in Cancer
In oncology, antibodies can activate immune responses against tumors. Checkpoint inhibitor antibodies are a prime example. Drugs like pembrolizumab (anti‑PD‑1) and ipilimumab (anti‑CTLA‑4) bind inhibitory receptors on T cells, preventing tumor cells from switching off the immune attack. By blocking these “brakes,” checkpoint antibodies boost the patient’s own T cells to destroy cancer cells, improving survival across multiple cancers. Notably, FDA-approved antibodies targeting PD-1/PD-L1 and CTLA-4 have achieved remarkable success across multiple cancers, significantly improving patient survival.
Targeted Cell Depletion
A third major use of therapeutic antibodies is targeting specific cells for destruction. Certain mAbs recognize antigens on the surface of diseased cells (for example, a protein on cancerous or autoimmune B cells) and flag those cells for elimination. A classic case is rituximab, which targets the CD20 antigen on B lymphocytes. By binding CD20, rituximab marks B cells for attack by the immune system and leads to their depletion. This mechanism is effective for treating B-cell malignancies like lymphomas, and it also helps quell autoimmune diseases where misdirected B cells produce pathogenic antibodies. Dozens of antibodies using similar “targeted cell killing” strategies are in clinical use. In total, over 160 monoclonal antibody drugs have been approved for human therapy as of 2023, ranging from anticancer agents to biologics for asthma, migraine, and high cholesterol.
Emerging Innovations and Future Directions
Novel Antibody Formats (Nanobodies and Beyond)
Researchers are engineering novel antibody formats beyond the classic Y-shaped IgG. Nanobodies, for instance, are tiny single-domain antibodies derived from camelid or shark immunoglobulins that retain full antigen-binding ability in a fragment a fraction of the size. These heavy-chain-only antibodies are extremely stable and can bind unique concave epitopes. Such features make them attractive for detecting tricky targets and even for drug delivery. Dozens of nanobody-based therapeutics and imaging agents are now in development.
Bispecific and Multispecific Antibodies
Another innovation is bispecific antibodies that bind two different targets at once. By having dual specificity, one antibody can bridge cells or pathways, for example, bringing a T cell into contact with a tumor cell to stimulate directed killing. Telitacicept, recently approved in China for lupus, is a dual‑ligand fusion protein that traps BAFF (BLyS) and APRIL rather than a conventional bispecific IgG.
AI-Guided Discovery and Sequence Optimization
Beyond new antibody structures, cutting-edge methods are improving how we discover and produce antibodies. Techniques like phage display allow scientists to screen vast libraries to find antibodies with high affinity and specificity. Furthermore, artificial intelligence (AI) and directed evolution are being applied to optimize antibody sequences.
At Ziab, we build on these advances with a proprietary platform that designs high‑affinity nanobodies entirely in silico, without animal immunization. Our automated laboratories then express and purify the selected sequences within days. Each nanobody is roughly one-tenth the size of a conventional antibody, and preclinical data show superior tissue penetration, including measurable levels beyond the blood‑brain barrier and inside dense tumor microenvironments. We use AI to fine‑tune every sequence for stability and consistent manufacturing, cutting much of the trial and error seen in traditional workflows. The result is a pipeline of binders that reach previously “undruggable” targets in neurology and oncology.
Next-Generation Diagnostic Platforms
On the diagnostics front, antibody-based tests are becoming more sensitive and user-friendly. Innovations in assay design, such as incorporating nanomaterials for signal amplification, are pushing detection limits closer to the single-molecule level.
Point-of-care diagnostics are being refined for greater accuracy. Upcoming lateral flow assays integrate smartphone cameras and novel labels (like fluorescent or plasmonic nanoparticles) to quantify results and transmit data. These advancements aim to redefine accessibility of diagnostics, integrating rapid antibody tests into routine health management and public health surveillance. The COVID-19 pandemic showcased how quickly antibody tests can be deployed. Now, improved formats promise even broader use for home testing and field diagnostics.