Submitted May 14, 2007
Accepted July 3, 2007
CD45RO enriches for activated, highly mutated human germinal center B cells
Stephen M. Jackson, Natessa Harp, Darshna Patel, Jeffrey Zhang, Savannah Willson, Yoon J. Kim, Christian Clanton, and J Donald Capra*
Molecular Immunogenetics Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK, United States
* Corresponding author; email: jdonald-capra{at}omrf.ouhsc.edu.
To date, there is no consensus regarding the influence of different CD45 isoforms during peripheral B cell development. Examining correlations between surface CD45RO expression and various physiological processes ongoing during the germinal center reaction, we hypothesized that GC B cells, like T cells, that upregulate surface RO should progressively acquire phenotypes commonly associated with activated, differentiating lymphocytes. GC B cells (IgD-CD38+) were subdivided into three surface CD45RO fractions; RO-, RO+/-, and RO+. We show here that the average number of mutations per IgVH transcript increased in direct correlation with surface RO levels. Conjunctional use of RO and CD69 further delineated low/moderately and highly mutated fractions. AID mRNA was slightly reduced among RO+ GC B cells suggesting that higher mutation averages are unlikely due to elevated somatic mutation activity. Instead, RO+ GC B cells were negative for annexin V, comprised mostly (93%) of CD77- centrocytes, and were enriched for CD69+ cells. Collectively, RO+ GC B cells occupy what seems to be a specialized niche comprised mostly of centrocytes that may be in transition between activation states. These findings are among the first to sort GC B cells into populations enriched for live mutated cells solely using a single extracellular marker.
