In Vitro Generation of Long-lived Human Plasma Cells

Abstract

Plasma cells (PCs), the terminal effectors of humoral immunity, are short-lived unless supported by niche environments in which they may persist for years. No model system has linked B cell activation with niche function to allow the in vitro generation of long-lived PCs. Thus, the full trajectory of B cell terminal differentiation has yet to be investigated in vitro. In this article, we describe a robust model for the generation of polyclonal long-lived human PCs from peripheral blood B cells. After a proliferative plasmablast phase, PCs persist in the absence of cell division, with viability limited only by elective culture termination. Conservative predictions for PC life expectancy are 300 d, but with the potential for significantly longer life spans for some cells. These long-lived PCs are preferentially derived from memory B cells, and acquire a CD138high phenotype analogous to that of human bone marrow PCs. Analysis of gene expression across the system defines clusters of genes with related dynamics and linked functional characteristics. Importantly, genes in these differentiation clusters demonstrate a similar overall pattern of expression for in vitro and ex vivo PCs. In vitro PCs are fully reprogrammed to a secretory state and are adapted to their secretory load, maintaining IgG secretion of 120 pg/cell/day in the absence of XBP1 mRNA splicing. By establishing a set of conditions sufficient to allow the development and persistence of mature human PCs in vitro, to our knowledge, we provide the first platform with which to sequentially explore and manipulate each stage of human PC differentiation.

A proliferation-inducing ligand sustains the proliferation of human naïve (CD27−) B cells and mediates their differentiation into long-lived plasma cells in vitro via transmembrane activator and calcium modulator and cyclophilin ligand interactor and B-cell mature antigen

“…First, we demonstrated upregulated expression of the surface antigen CD138 and increased secretion of IgG by the B cells as differentiation progressed. This is consistent with evidence showing that CD138 expression increases gradually as PCs mature [24,38,39]. Additionally, we observed the effect of APRIL on each differentiation stage of naïve (CD27 À ) B cell in vitro.…”

“…Human memory B cells differentiate into long-lived PCs in vitro [24]. In contrast, Huggins et al [23] differentiated human naïve (CD27 À ) B cells into CD138 + PCs but did not show that these cells differentiated into long-lived PCs in vitro.…”

“…Further, memory B cells differentiate into long-lived PCs when cultured in the presence of supernatants from the bone marrow-derived stromal cell line M2-10B4 [24], which supports long-term culture of human bone marrow stem cells. How M2-10B4 cells contribute to the survival of PCs is unknown, but memory B cells may require well-balanced support from stromal cells [31,[59][60][61].…”

“…Huggins et al [23] demonstrated that naïve B cells can differentiate into PCs after addition of a CpG-ODN, CD40L, IL-2, IL-6, IL-10, IL-15, and hepatocyte growth factor (HGF) in a three-step culture system, and that the induced PCs express CD138. Cytokines such as IL-6, insulin-like growth factor-1, and HGF are secreted by bone-marrow stromal cells, and the local environment in the bone marrow is thought to support the survival of PCs [24]. Our group recently reported an immunosuppressive agent susceptibility for the differentiation of human B (CD19 + ) cells in vitro that employs IL-21, CD40L, and CpG-ODNs.…”

Hypoxia favors the generation of human plasma cells

“…3,4 Recently, we and others also demonstrated that IL-6 in combination with APRIL, BAFF, or soluble stromal cell factors supports the generation and survival of long-lived PCs (LLPCs). 5,6 In mammals, oxygen distribution is robustly regulated by the vascular system, which continually distributes oxygensaturated red blood cells throughout the body. Despite the sturdiness of this system, oxygen distribution in the body is not uniform.…”