B cells are part of adaptive immune system. They secret antibodies (IgM, IgG, IgA, IgE) and can present processed antigens to CD4 T cells. However, beyond these functions, nothing much is known about B cells.
Studies on CD4 helper T cells, on the other hand, has uncovered and characterized multiple individual subsets ranging from Th1 to Th17.
Still, occasionally, one can come across of new paper in top journals (weird!) describing some new role of B cells that do not fit into current paradigm. Such example, for example, includes GM-CSF producing IRA B cells. In addition, there are plenty reports of IL-10 producing B cells involved in T cell suppression. Usually, immunologists would say “that’s weird” and then forget about it.
So why are research on B cells lagging so far behind the T cell’s studies?
One explanation has to do with the fact that unlike T cells, B cells do not survive well in an in vitro culture. One can re-stimulate T cells in vitro over and over again and they will still continue to expand (this is how originally Th1 and Th2 clones were derived). However, culture conditions developed for B cells thus far stimulate them to develop into short-term antibody-secreting cells (plasmablasts or plasma cells) which finally will die, usually within 2 weeks of initiation of B cell culture. There is one report describing culture condition where the authors were able to maintain plasma cells for 60 days in vitro. But plasma cells are not B cells.
The real issue with B cells studies is the fact that we actually do not know how B cells survive in vivo. We don’t know what are the combination of stromal cells or cytokines that can provide tonic, survival signals to B cells. We don’t even know what is the role of surface IgM receptors in B cells survival in vivo.
Basically, we have an incomplete view of B cells biology. I think time has come to go back and re-evaluate our models for B cells. Without conceptual progress in B cells biology we will be just scratching our heads every time we hear some new research describing novel non-conventional B cell function.
posted by David Usharauli