Presence of Two Different Immunoglobulin Heavy Chains in Individual Cells of Established Human Hematopoietic Cell Lines

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Abstract
Summary: Presence of γ-, α- and µ-heavy chains of immunoglobulin was examined in cultured cells of established human hematopoietic cell lines. Combinations of a fluorescein-conjugated antibody of one specificity and a tetramethylrhodamine-conjugated antibody of another specificity were used to see whether individual cells contain heavy chains of more than one class. Studies were concentrated on two cell lines which produced immunoglobulins of more than one class. Essentially all the immunoglobulin-containing cells in cell line LK1D (RPMI no. 4292) were found to contain both γ- and α-heavy chains. Individual cells containing both γ- and α-heavy chains were also found in high proportions in cell line RPMI no. 3157 along with the cells containing only γ-, only α- or only µ-chains. There were a few cells containing both γ- and µ-chains, but no cells were found to contain both α- and µ-chains. In addition to the usual controls for fluorescent antibody techniques, specificity of antibody reagents was shown by staining bone marrows from myeloma patients and a mixture of cells from two cell lines, one producing only IgA and the other producing only IgG. Even when the cells of these two cell lines were grown together in the same culture, no cells were found to contain two heavy chains. This strongly suggests that the chains found in individual cells are being synthesized in the cells and are not derived from other cells in the culture. Antibody reagents were specifically purified and were made monospecific to each heavy chain of immunoglobulin by the use of insoluble immunoadsorbents conjugated with homologous or heterologous antigens.