RT Journal Article SR Electronic T1 Delineation and characterization of human B cell subpopulations at various stages of activation by using a B cell-specific monoclonal antibody. JF The Journal of Immunology JO J. Immunol. FD American Association of Immunologists SP 4027 OP 4034 VO 136 IS 11 A1 Kikutani, H A1 Nakamura, H A1 Sato, R A1 Kimura, R A1 Yamasaki, K A1 Hardy, R R A1 Kishimoto, T YR 1986 UL http://www.jimmunol.org/content/136/11/4027.abstract AB Human tonsillar B cells were separated into three distinct subpopulations, Ba-/IgD+, Ba+/IgD+, and Ba+/IgD-, by using a B cell-specific monoclonal antibody (anti-Ba) that recognizes only activated B cells, and anti-IgD antibody. Stimulation of Ba-/IgD+ cells with anti-mu plus PHA-conditioned culture supernatant (PHA-sup) or TPA induced Ba+/IgD+ cells, which reverted to Ba-/IgD+ phenotype in the absence of continuous stimulation. Further stimulation of Ba+/IgD+ cells with several B cell activators, such as TPA plus anti-mu or PWM plus T cells, resulted in the loss of IgD expression. Three-color FACS analysis showed that the expression of transferrin receptor (TFR) was at its maximum in Ba+/IgD- cells, and the intensity of this expression was proportional to that of Ba expression in Ba+/IgD+ cells. PHA-sup induced maximum proliferation in Ba+/IgD- cells, and the degree of response was a function of the intensity of Ba expression in Ba+/IgD+ cells. PHA-sup or purified BCDF (BSF-2) induced Ig secretion preferentially in Ba+/IgD- cells. Taken together, these results show that resting B cells (Ba-/IgD+) are activated into Ba+/IgD+ cells, and then into Ba+/IgD- cells, under mitogenic stimulation, and BCDF induces the final maturation of Ba+/IgD- cells into Ig-secreting cells. Ba+/IgD- cells, which maximally expressed TFR as well as Ba and displayed maximum proliferative response to PHA-sup, did not express any Tac antigen. On the other hand, in vitro activated B cells expressed Ba and TFR as well as Tac antigen.