Cell typing with monoclonal antibodies to CD antigens in flow cytometry or other immunological applications can give false positives in the absence of proper controls. Sigma recommends using a non-reactive immunoglobulin of the same isotype and concentration to detect non-specific binding. We offer purified monoclonal mouse immunoglobulins of isotypes IgG1, IgG2a, IgG2b, and IgM. Each is available both unlabeled and conjugated to fluorescein isothiocyanate(FITC). Mouse IgG1 conjugated to phycoerythrin is also available.