ELISA is a fundamental immunoassay technique widely used in biological experiments, scientific research testing and clinical laboratory diagnosis. Beginners often get confused about its principles, workflows, classifications, detection range and other basic concepts. This article organizes core ELISA knowledge in a FAQ format to cover common blind spots and help novice researchers quickly master key points of ELISA.
Coating is the fundamental core step of ELISA experiments. Essentially, it immobilizes specific antibodies or antigens onto the surface of a solid‑phase carrier to build an exclusive antigen‑antibody reaction platform. The quality of coating directly determines the sensitivity, specificity and reproducibility of the whole assay. Many abnormal ELISA results originate from improper coating operations. This FAQ document sorts out principles of coating, key influencing factors, blocking procedures, and the differences between in‑house coated plates and commercial pre‑coated kits, to help researchers troubleshoot common coating‑related experimental problems.
This article organizes FAQs for high-frequency issues in double-antibody sandwich ELISA experiments, covering pre-experiment preparation, complete operational points, data processing, and common fault analysis. It aims to help experimenters quickly identify problems, standardize experimental procedures, reduce experimental failures, and obtain stable and reliable detection data.
Enzyme-Linked Immunosorbent Assay (ELISA) is a classical immunoassay technology that relies on antigen-antibody specific binding, immobilizing soluble antigens/antibodies on solid-phase microplates, and utilizes signal amplification through enzyme-catalyzed substrate chromogenic reactions for qualitative and quantitative detection of trace substances in biological samples.
TMB (3,3',5,5'-tetramethylbenzidine) is the most commonly used chromogenic substrate in enzyme-linked immunosorbent assays, relying on horseradish peroxidase to catalyze the color reaction. It is widely used in conjunction with ELISA, immunohistochemistry, and other immunoassay labeling experiments, directly determining the sensitivity, reproducibility, and reliability of the test data. In actual experiments, any improper operation in TMB reagent storage, sample addition and plate washing, incubation control, or environmental interference can cause various abnormal issues such as high background, no color development, well-to-well color differences, reading fluctuations, and premature reagent oxidation and deterioration, greatly increasing the cost of repeated experiments and even rendering clinical or research sample data invalid.
Natural killer (NK) cells represent a vital subset of lymphocytes that constitute the body’s innate immune defense system. These large granular lymphocytes carry abundant cytoplasmic granules, sharing partial morphological features with monocytes. NK cells possess direct cytotoxic capability against abnormal target cells, serving critical roles in antiviral defense, immune surveillance and tumor suppression. In addition, they secrete functional cytokines such as IFN-γ to regulate hematopoiesis, inflammatory responses and systematic immune reactions.
Stem cells represent a special cell population featuring self-renewal capacity, robust proliferative activity and multidirectional differentiation potential. Based on developmental origins, they are categorized into embryonic stem cells (ESCs) and adult stem cells (ASCs). Embryonic stem cells possess totipotency and unlimited proliferative capacity, capable of generating all somatic cell subtypes; this group includes embryonic stem cells and embryonic germ stem cells. Adult stem cell subtypes cover neural stem cells, hematopoietic stem cells, bone marrow mesenchymal stem cells and epidermal stem cells, among others.
Vascular endothelial growth factor (VEGF), also known as vascular permeability factor (VPF), is a dimeric glycoprotein ligand that activates a complex signal transduction network responsible for new blood vessel formation. Once VEGF binds to cell surface VEGF receptors (VEGFRs), the intracellular tyrosine kinase domains become activated, triggering sequential signaling events that regulate vasculogenesis and angiogenesis processes.
Tumor Necrosis Factor (TNF, commonly abbreviated as TNFα) is a cytokine that selectively eliminates tumor cells without producing prominent toxic effects on normal healthy cells. It functions as an intracellular signaling mediator that modulates systemic inflammation and constitutes one of the key cytokine components that initiate the organism’s acute‑phase response.
The transforming growth factor beta (TGF‑β) signal cascade refers to a complete set of intracellular signal transmission events triggered by TGF‑β ligands. This signaling axis performs irreplaceable regulatory functions across numerous biological activities, including cell division, extracellular matrix synthesis, cell fate differentiation, programmed cell death, embryonic morphogenesis, organ construction, immune homeostasis and inflammatory reactions.