Abstract
Mouse myeloma cells have been stained in suspension at 0 °C or at room temperature with fluorescein‐labeled rabbit anti‐mouse immunoglobulin sera (F‐RAMIG) or with unlabeled RAMIG followed by fluorescein‐labeled goat anti‐rabbit immunoglobulin sera (F‐GARIG). Tissue culture adapted murine myeloma cells 5563 (IgG~2a~κ) have been used most extensively in these studies. 95–100 % of the cells show surface fluorescence at both temperatures after staining with F‐RAMIG or with RAMIG followed by F‐GARIG. At 0 °C the staining is diffuse over all the surface, at room temperature the staining is much brighter and patchy. The nature of the H and L‐chains at the surface of the myeloma cell is shown to parallel the type of secretory product. Thus, 5563 cells stain brilliantly with anti‐IgG and anti‐κ chain sera, but not at all with anti‐μ or anti‐α chain sera, which respectively stain TEPC 183 (IgMκ) and MOPC 47A (IgAκ) cells brilliantly. Also, MOPC 315 cells (IgAλ) do not stain with antisera against 5563 myeloma protein, but do stain with antisera against MOPC 47A and MOPC 104E myeloma proteins.
Immediately after staining at 0 °C or room temperature, the fluorescence is located over the whole surface. However, if the stained cells are incubated at 37 °C in tissue culture medium, the stain gradually localizes to one pole of the cell such that by 5 h, about 50 % of the cells show staining localized to one hemisphere. The presence of the RAMIG‐antigen complex seemed to have little or no effect on the rate of secretion of myeloma protein during a 5 h period. The results are discussed in relation of the findings of others and to the significance of the surface immunoglobulin of myeloma cells.