Unconjugated anti-human primary antibodies are purified immunoglobulins that bind specifically to human antigens but carry no covalently attached reporter molecule, such as a fluorophore, enzyme, or biotin tag. They are also commonly referred to as "purified" antibodies, although the term "unconjugated" explicitly emphasizes the absence of a detection label. Because they lack a built-in reporter, these antibodies require a secondary detection reagent—typically an anti-species antibody conjugated to a fluorophore or enzyme—to visualize or quantify antigen binding. This label-free format offers maximum flexibility in assay design and serves as the starting material for custom conjugation to a wide range of labels.
Production and Purification
Unconjugated anti-human antibodies are generated by immunizing a host species, most commonly goat, rabbit, mouse, rat, or chicken, with a purified human protein or whole human immunoglobulin. Monoclonal antibodies are produced from hybridoma cell lines or recombinant expression systems, while polyclonal antibodies are harvested from serum. Purification is critical to remove non-immunoglobulin proteins, contaminants, and non-specific antibodies. The most widely used method is affinity chromatography with immobilized Protein A, Protein G, or Protein L, which selectively binds the Fc region of immunoglobulins. For higher specificity, antigen-affinity purification is employed, in which the target antigen is immobilized on a solid support and the antibody is eluted after binding. Additional methods include ion-exchange chromatography, size-exclusion chromatography, and ammonium sulfate precipitation. Purified antibodies are typically formulated in phosphate-buffered saline (PBS) at concentrations of 0.1–1 mg/mL, often supplemented with bovine serum albumin (BSA) and sodium azide as stabilizers. They should be stored at 2–8°C and should not be frozen, as freezing can cause aggregation and loss of activity.
