The effect of interferon-alpha on the ecto 5'-nucleotidase of human lymphoblastoid B-cell lines depends on the class of immunoglobulin secreted.

Thirteen immunoglobulin-secreting mycoplasma-free human cell lines were treated with increasing concentrations of lymphoblastoid interferon-alpha (IFN-alpha) in order to study the activity of their CD73 ecto-5'-nucleotidase (5'N), their rate of growth and their immunoglobulin (Ig) production. Although IFN-alpha did not immediately affect the activity of the 5'N on the cell plasma membranes, the class of Ig secreted by the cell lines determined whether culturing the cells in the presence of IFN-alpha gave a small increase in the 5'N enzyme activity (IgM), or had no effect (IgE), or showed a marked decrease in activity (IgG). The 5'N activity of two IgG4-secreting clones was more suppressed by IFN-alpha than that of the four IgG1-secreting clones. The clone with the highest 5'N was killed by IFN-alpha. A high 5'N activity inhibited the growth rate of the cells, since the rate of growth of the three IgG-producing lines with high 5'N was increased when their 5'N was inhibited by increasing concentrations of IFN-alpha. The growth rate of three other Ig-producing lines was uninhibited by up to 10(5) U/ml IFN-alpha, whereas the rest were partially or strongly inhibited. Excluding the clone which died, 10/11 lines or cultures increased their Ig/cell by a mean of 25% at 100 U/ml IFN-alpha; their total Ig production also increased despite any growth inhibition. One IgG-secreting clone decreased its Ig production at 100 U/ml IFN-alpha by 11%. The Ig/cell of 4/5 of the cell lines increased with IFN-alpha concentrations up to at least 10(4) U/ml. The increase in Ig/cell was not related to the class of Ig, the growth rate of the cells or the amount of 5'N.