Regulation of Growth and Differentiating of Pre‐Activated B Lymphocytes

Abstract

The differential effects of H-2 IAk-specific T helper cells, their soluble factors and Sepharose-coupled anti-mu antibodies on the growth and differentiation of pre-activated B cells were studied. It was found that the prolonged growth of pre-activated B cells required activation signals from major histocompatibility complex (MHC)-restricted T helper cells or Sepharose-coupled anti-mu antibodies. The MHC-restricted T helper cells induced both prolonged growth and differentiation of activated B cells. Anti-mu antibodies together with T helper cell-derived soluble factors induced prolonged growth of activated B cells, but no differentiation into Ig secretion was detected. The inhibition of Ig secretion in anti-mu cultures could be overcome to some extent by either MHC-restricted T helper cells or lipopolysaccharide together with soluble factors. It was also observed that T helper cell interactions were needed for long-term in vitro culture of pre-activated B lymphocytes.

Regulation of B cell growth and differentiation via CD21 and CD40

“…The apparent block of B cell differentiation induced by the anti-CD40 antibody even in the presence of CS was reminiscent of the effect previously observed with anti-Ig stimulation [19,261. This result, therefore, prompted us to investigate whether a CD40 signal would down-regulate B cell differentiation in a more general way.…”

“…This scenario is unlikely since the CD21 signal is qualitatively distinct from an anti-Ig signal with regard to the induction of B cell differentiation to Ig secretion. Thus, cross-linking of sIg inhibits Ig secretion [19,261, while anti-CD21-Sepharose alone induced significant numbers of PFC, and even more efficiently in the presence of a CD40 signal. These data are in agreement with the findings in the human system where signaling via CD21 induced a plasmacytoid phenotype in GC B cells [8, 91. In the mouse, however, the effect of the CD21 signal appears not to be dependent on the presence of cytokines and is not markedly enhanced by their addition.…”

“…Antibody to CD21 was 7G6 [22], anti-x was 187.1 [23], while B3/B4 was used as an anti-CD23 reagent [24]. Purified antibodies were coupled to the Sepharose beads as described [19] and used at a final concentration of 1 % in stimulation experiments. Anti-CD21 mAb was biotinylated and anti-CD23 mAb was FITC-conjugated according to standard protocols.…”

Phenotypic Convergence and Divergence of Surface Immunoglobulin and CD40 Signals

“…For RNA cultures splenic cells were cultured at 10 6 cells/ml in six-well plates in RPMI-1640 supplemented with 7.5% fetal calf serum. As T helper cells an irradiated (3000 rad) alloreactive (BALB/k anti-BALB/c) T helper cell line was established as described [15]. For prestimulation experiments B cells were cultured as described earlier [16].…”

Cell‐Cycle Kinetics of Proliferating Mouse B Lymphocytes In Vitro

“…Tissue culture conditions. Resting splenic B cells were prepared as described [10] and stimulated in vitro with either LPS (£. <:o//005:B5, Difco, Detroit, MI.…”