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. Author manuscript; available in PMC: 2015 Jan 16.
Published in final edited form as: Acta Neuropathol. 2014 Jul 4;128(2):177–190. doi: 10.1007/s00401-014-1313-z

Figure 2. B lymphocyte compartmentalization, development, and differentiation.

Figure 2

In adult mammals, B lymphocytes common lymphocytes progenitors (CLP) originate in the bone marrow, where they develop into Pro-B cells, Pre-B cells, and immature B cells. As part of their life cycle, immature B cells that possess a mature B cell receptor (BCR) and chemokine receptors, egress from the bone marrow into lymphatic vessels. Once within the afferent lymphatics, these cells by definition are considered mature naïve B cells. In the lymph node, there a very heterogeneous groups of B lymphocytes, including marginal zone B cells, B1 cells, B regulatory cells, transitional B cells, mature B cells, memory B cells, as well as short-lived plasma cells, and plasmablasts. The CD19 antigen is a type I transmembrane glycoprotein that belongs to the immunoglobulin Ig superfamily. It is expressed throughout B-cell development, including early pro-B cells and late pro-B cells, as well as in memory B cells, plasmablasts, and a proportion of plasma cells. The overall expression increases approximately threefold as B cells mature. In terminally differentiated plasma cells, which are highly prevalent in the bone marrow, CD19 can no longer be detected.