AtaGenix Laboratories
AtaGenix Laboratories
Release time: 2026-04-03 View volume: 2
Antibody isotyping determines the class and subclass of an antibody’s heavy chain. Different isotypes have distinct effector functions, half-lives, and application suitabilities — making isotype identification an essential step in antibody characterization.
Isotyping identifies the heavy chain class (IgG, IgM, IgA, IgD, IgE) and, for IgG, the subclass (IgG1, IgG2a, IgG2b, IgG3 in mouse; IgG1, IgG2, IgG3, IgG4 in human). It also determines the light chain type (κ or λ). Isotype is determined by the constant region sequence, which dictates Fc receptor binding, complement activation, and serum half-life.
| Subclass | ADCC | CDC | Protein A Binding | Typical Use |
|---|---|---|---|---|
| IgG1 | Moderate | Strong | Yes | Most common mAb subclass; WB, IHC, ELISA, in vivo |
| IgG2a | Strong | Strong | Yes | Strongest effector function; preferred for in vivo depletion |
| IgG2b | Moderate | Moderate | Yes | Intermediate effector function; general research use |
| IgG3 | Weak | Strong | No (use Protein G) | Less common; avoid for Protein A purification |
| IgM | No | Very strong | No | Early immune response; pentameric, high avidity but low affinity per site |
ELISA-based isotyping: The most common method. Capture antibody with anti-mouse Ig, then detect with subclass-specific secondary antibodies (anti-IgG1, anti-IgG2a, etc.). Fast and quantitative.
Lateral flow isotyping strips: Rapid (<10 min) qualitative result. Convenient for hybridoma screening but less sensitive than ELISA.
Mass spectrometry: Definitive identification for ambiguous cases, especially when ELISA gives mixed signals (biclonal hybridomas).
Isotype determines which purification method to use (Protein A works for IgG1/2a/2b but not IgG3 or IgM), which secondary antibody to select for detection, and whether the antibody has the right effector functions for in vivo use. For therapeutic antibody development, isotype choice directly impacts ADCC, CDC, and half-life, making it a key engineering parameter.
AtaGenix provides isotype determination as part of every hybridoma and monoclonal antibody development project, with full isotype reports included in standard deliverables.
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