Characterization of B and plasma cells in blood, bone marrow, and secondary lymphoid organs of rhesus macaques by multicolor flow cytometry.

Abstract

B cells, as an important part of the humoral immune response, are generated in the BM, migrate to secondary lymphoid organs, and upon activation, differentiate into antibody-producing memory B cells or plasma cells. Despite the pivotal roles that they play in different diseases, a comprehensive characterization in healthy rhesus macaques, which serve as valuable models for a variety of human diseases, is still missing. With the use of multiparameter flow cytometry, we analyzed B cells in BM collected from two locations, i.e., the iliac crest (BMca) and the femur (BMfem), PB, as well as secondary lymphoid organs of healthy rhesus macaques. We assessed the frequencies of immature and mature B cells, as well as CD19(+) CD20(-) CD38(+/++) CD138(+/++) plasmablasts/plasma cells. Furthermore, we found site-specific differences in the expression of markers for B cell activation and proliferation, chemokine receptors and Igs, as well as the distribution of memory B cell subpopulations. As secondary lymphoid organs harbor the highest frequencies of naive B cells, expression of CD80, CD95, and Ki67 was lower compared with B cells in the periphery and BM, whereas expression of IgD, CXCR4 (CD184), and CCR7 (CD197) was higher. Interestingly, BMca differed from BMfem regarding frequencies of B cells, their expression of CD80 and CXCR4, T cells, and plasma cells. In summary, these data identify baseline values for the above-mentioned parameters and provide the foundation for future studies on B and plasma cells in different diseases.