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When labeled secondary antibodies specific for both heavy and light chains of IgG, e.g. anti-IgG (H+L), are used to detect protein bands on Western blots following immunoprecipitation (IP), two heavy bands appear (Figure A) corresponding to the heavy (50 kDa) and light chains (25 kDa) of the precipitated primary antibody. These bands usually obscure detection of any protein of interest with a molecular weight near 50 kDa or 25 kDa. However, when labeled anti-IgG, Light Chain Specific antibodies are used for detection, they bind only to the light chain band on the blot (Figure B) and to light chains on the native primary antibodies used for detection. Therefore, a 50 kDa protein may be detected on blots without interference from the precipitated IgG in the same band by incubation with its unlabeled primary antibody followed by labeled anti-IgG, Light Chain Specific. Similarly, a 25 kDa protein may be detected after IP without interference by using its unlabeled primary antibody followed by labeled anti-IgG, Fc fragment specific.
Anti-IgG, Light Chain Specific antibodies also have been thoroughly adsorbed to minimize cross-reactivity with immunoglobulins from other species which may be present on blots.
Although the antibodies react strongly with native IgG light chains, some do not react as strongly with reduced and denatured light chains. Therefore, they are not recommended for sensitive detection and quantitation of reduced and denatured light chains on Western blots.