The Journal of Immunology, Vol 133, Issue 4 1896-1901, Copyright © 1984 by American Association of Immunologists

ARTICLES

Human tonsil B lymphocyte function. II. Pokeweed mitogen-induced plasma cell differentiation of B cell subpopulations expressing multiple heavy chain isotypes on their surface

GC Mudde, CJ Verberne and GC de Gast

Human tonsil non-T cells were successfully separated into surface IgM+G- ve (sIgM+G-), sIgM+G+, sIgM-G-, and sIgM-G+ B cell fractions. The two- step separation technique used did not affect the pokeweed mitogen- (PWM) induced plasma cell differentiation of the B cells. The highest percentages of plasma cells after PWM stimulation were found in the sIgM- fractions, and the lowest percentage was in the sIgM+G- fraction (20.8 +/- 2.3%), the latter predominantly cytoplasmic mu-chain-positive (c mu +) (84.1 +/- 3.5%) plasma cells. In this fraction, almost no c gamma + plasma cells were found. The sIgM+G+ produced c mu + (47.5 +/- 7.5%), c gamma + (35.7 +/- 5.8%), and c alpha + (16.8 +/- 4.0%) plasma cells. All three isotypes were found on the surface of the B cells in this fraction before PWM stimulation. The sIgM-G- fraction contained about 10% plasma cells before stimulation, which were predominantly c gamma +. After PWM stimulation, primarily c alpha + (64.2 +/- 4.3%) plasma cells were found. The sIgM-G+ fraction produced both c gamma + (75.0 +/- 2.3%) and c alpha + (24.1 +/- 2.5) plasma cells. A mu to gamma class switch did not occur in vitro in the sIgM+G- fraction on PWM stimulation, and the sIgM+G+ fraction did not complete in vitro the mu to gamma switch it had started in vivo.