CD40 Stimulation of Human Peripheral B Lymphocytes: Distinct Response from Naive and Memory Cells

Abstract

During secondary immune response, memory B lymphocytes proliferate and differentiate into Ig-secreting cells. In mice, the binding of CD40 by CD154 clearly enhances the activation and differentiation of memory B lymphocytes. In humans, the role of CD40-CD154 in the stimulation of memory B lymphocytes is not as obvious since in vitro studies reported positive and negative effects on their proliferation and differentiation in Ig-secreting cells. In this study, we examine the response of peripheral memory and naive cells in relation to the duration of CD40-CD154 interaction. We measured the proliferation and differentiation of both subsets stimulated with CD154 and IL-4 for short- (4–5 days) and long-term (>7 days) periods. Following short-term stimulation, memory B lymphocytes did not expand but represented the only subset differentiating into IgG- and IgM-secreting cells. A longer stimulation of this population led to cell death, while promoting naive B lymphocyte proliferation, expansion, and differentiation into IgM- or IgG-secreting cells. This prolonged CD40 stimulation also triggered naive B lymphocytes to switch to IgG and to express CD27 even in absence of somatic hypermutation, suggesting that these latter events could be independent. This study suggests that naive and memory B lymphocytes have distinct requirements to engage an immune response, reflecting their different roles in humoral immunity.

c-Src tyrosine kinase co-associates with and phosphorylates signal transducer and activator of transcription 5b which mediates the proliferation of normal human B lymphocytes

“…For instance, CD40 activation through CD154 in the presence of IL-4 can induce proliferation and differentiation distinctively of peripheral human B lymphocyte subpopulations [7]. The mechanism by which normal human B lymphocytes proliferate to external signals is, however, not entirely clear.…”

“…However, using a combination of CD40 stimulation in the presence of interleukin (IL)-2, IL-4 and IL-10 appears to be a good stimulus for expansion of human and other animal B lymphocytes in vitro [7][8][9][10], and also plays a significant role in the normal development and function of B lymphocytes [11][12][13][14] as well as in the propagation of malignant B lymphocytes [15]. The exact signalling pathways responsible for the induction and maintenance of B lymphocytes proliferation are unknown, but previous studies have implicated a role for the c-Src protein tyrosine kinase [9].…”

CD40-activated B cells from patients with systemic lupus erythematosus can be modulated by therapeutic immunoglobulins in vitro

“…Leukocytes from healthy individuals were recovered from leukoreduction systems, as described previously (Néron et al 2006;Néron et al 2007), after informed consent and following approval by the Research Ethics Committee of Héma-Québec. Peripheral blood mononuclear cells (PBMCs) were prepared from patients and controls by density centrifugation over Ficoll-Paque (GE Healthcare Bio--Sciences Inc., Baie d'Urfé, QC, Canada) (Fecteau and Néron 2003) and stored frozen until B-cell purification. About 50-100×10 6 cells were recovered from each SLE sample.…”

“…For IVIg--treated cells, the assayed IgG and IgM concentrations in the last washing supernatants were found to be negligible in all cases (<5-10 ng/ml/h). Cells were seeded at 1-2×10 6 cells/ml in IMDM medium without added cytokines and CD154-expressing cells for 6-24 h. IgG and IgM concentrations were determined using a standard ELISA (Fecteau and Néron 2003).…”

“…3). To visualize whether there was a difference related to the level of activation, cell culture was performed under conditions of high CD40 stimulation in the presence of IL-4 alone (Fecteau and Néron 2003) and with low CD40 stimulation in the presence of IL-2, IL-4, and IL-10 ( Néron et al 2005). Overall, IVIg inhibited the expansion of HC and SLE B cells under both the high (2-to 4-fold) and low (1.5-to 2.5-fold) CD40 stimulation conditions (Figs.…”