T-Cell regulation of B-lymphoblastoid cell line function

Lymphokine factors inducing IgG production in human B-cell line ARH-77 and stimulatory effects of phorbol ester tumor promoter

Regulation of immunoglobulin-secreting cells (ISC) was studied in human IgG B-cell line ARH-77, as assayed by reverse plaque formation. Numbers of ISC were stimulated by both lymphokine (stimulation index = 1.5-8.7) and phorbol myristic acetate (PMA) (stimulation index = 2.7-42). Incubation of ARH-77 with the two agents together caused additive or super-additive numbers of ISC, suggesting that they acted on this B cell via different mechanisms. B-cell-inducing factors stimulating IgG ISC in ARH-77 line were found at 20,000 and 40-60,000 molecular mass. The 20-KDa factor could be distinguished from IL-2 by affinity chromatography on blue agarose. Stimulated cells maintained their immunoglobulin class, and no evidence for isotype switching to IgM or IgA was detected using lymphokine or PMA. The cell line is a model for normal B lymphocytes which have been activated, for example, by Staphylococcus bacteria, to respond to T-cell factors.

IgM and IgG secretion in human B-cell lines regulated by B-cell-inducing factors (BIF) and phorbol ester

Human B-cell lines were screened for stimulation of immunoglobulin production by incubation with lymphokine (LK) or tumor promoter, phorbol myristic acetate (PMA). One group of lines had essentially no immunoglobulin-secreting cells (ISC) under any condition (less than 0.01%), detected by a reverse plaque assay. Another group of lines had high levels of ISC (greater than 5%) which was not increased substantially by inducing agents. In a third group of IgM and IgG lines, there were intermediate levels of ISC which could be increased by LK, PMA or both agents. No evidence for isotype switching in a number of stimulated IgM and IgG cell lines was detected. Clone SKW6.4 of an IgM line was highly responsive to a B-cell-inducing factor (BIF) in LK. BIF for SKW6.4 and IgG line ARH-77 was weakly binding to DEAE cellulose, about 20,000 mol. wt., and separable from IL-2 by blue agarose chromatography. IL-2 did not stimulate secretion in SKW6.4 with or without purified BIF. In Clone SKW6.4, BIF stimulated ISC per recovered cell up to 30-fold by day 1 of culture, and these plateau levels of about 6% ISC were maintained for longer than 4 days. Treatment of cells with BIF for less than 1 day was sufficient to produce maximum effect on this clone for the succeeding 4 days. Cells stimulated with BIF and then subcultured at day 3 without BIF showed ISC numbers increasing but at a slower rate than the total population, suggesting that the induced differentiation state is long-lived (half-life of % ISC greater than 6 days) and that ISC produce some daughter ISC.(ABSTRACT TRUNCATED AT 250 WORDS)

Tumor promoter phorbol myristic acetate stimulates immunoglobulin secretion correlated with growth cessation in human B lymphocyte cell lines

Immunoglobulin production by lymphoblast cell lines was studies using protein A-red blood cell plaque formation to detect individual secreting cells. Immunoglobulin (Ig) secretion by 6 of 12 human B-cell lines tested could be stimulated up to twentyfold by phorbol myristic acetate (PMA) at subtoxic concentrations of 10-1000 ng/ml depending on the line. Stimulation was found with both IgM and IgG cell lines. No switch of Ig class synthesis was found in the cell lines as a result of PMA incubation. Increase in Ig secretion was closely associated with cessation of growth resembling induction of terminal differentiation in the cells. PMA induction of Ig secretion in B lymphocytes from normal peripheral blood requires the cooperation of T cells. PMA stimulation of certain cell lines reported here suggests that the lines are late in the differentiation pathway to plasmacyte and can be easily triggered to secrete Ig by membrane-altering agents.