Isolation and Characterization of IgA Produced by an Established Human Lymphocytoid Cell Line¹ Free

Extracellular and intracellular human immunoglobulins of the IgA class were isolated in a highly purified state from the culture of an established human lymphocytoid cell line RPMI 4666. It was found that the general features of these immunoglobulins are similar to the serum IgA in myeloma individuals, consisting of covalently-bound α heavy chains and kappa light chains and possessing idiotypic antigenic determinants in addition to the antigenic determinants common to other κ type IgA. The extracellular immunoglobulin was found in both monomeric and dimeric forms while the intracellular immunoglobulin was found only in the monomeric form. Although the extracellular and intracellular immunoglobulins differed distinctly in their electrophoretic mobility, no difference could be detected in their antigenic determinants. The difference in their mobilities was shown to be reflected in their Fab-fragments.