Plasma cells (PCs), the end point of B-cell differentiation, are
a heterogeneous cell compartment comprising several cell subsets
from short-lived highly proliferative plasmablasts to long-lived
nondividing fully mature PCs. Whereas the major transcription
factors driving the differentiation of B cells to PCs were recently
identified, the subtle genetic changes that underlie the transition
from plasmablasts to mature PCs are poorly understood. We recently
described an in vitro model making it possible to obtain a large
number of cells with the morphologic, phenotypic, and functional
characteristics of normal polyclonal plasmablastic cells (PPCs).
Using Affymetrix microarrays we compared the gene expression profiles
of these PPCs with those of mature PCs isolated from tonsils (TPCs)
and bone marrow (BMPCs), and with those of B cells purified from
peripheral blood (PBB cells) and tonsils (TBCs). Unsupervised
principal component analysis clearly distinguished the 5 cell
populations on the basis of their differentiation and proliferation
status. Detailed statistical analysis allowed the identification
of 85 PC genes and 40 B-cell genes, overexpressed, respectively,
in the 3 PC subsets or in the 2 B-cell subsets. In addition, several
signaling molecules and antiapoptotic proteins were found to be
induced in BMPCs compared with PPCs and could be involved in the
accumulation and prolonged survival of BMPCs in close contact
with specialized stromal microenvironment. These data should help
to better understand the molecular events that regulate commitment
to a PC fate, mediate PC maintenance in survival niches, and could
facilitate PC immortalization in plasma cell dyscrasias.