Differential expression of GL7 activation antigen on bone marrow B cell subpopulations and peripheral B cells

GL7 was originally described as a 35-kDa late activation antigen on mouse T and B cells. GL7 expression has also been demonstrated on thymocytes, germ inal center B cells and some neuronal cell types. Flow-cytometry and immuno histochemistry were used to follow changes in the expression of GL7 during B cell development, amongst B cell subpopulations and various anatomical lo cations. GL7 is expressed as early as the pro-B cell stage and increases up to the pre-B-I stadium. Expression remains high on pre-B-II and on immatur e B cells, although slightly decreases during maturation. GL7 is almost com pletely downregulated when IgD appears on the cell surface. On the peripher y only a few B cells are positive and these cells are almost exclusively fo und in the sIgD(-) germinal center areas of lymph nodes and spleen. The sta ining pattern of GL7 is very similar to that of PNA in the lymph nodes but in the bone marrow we have found both B220(+)PNA(+)GL7(-) and B220(+)PNA(+) GL7(+) populations, showing that GL7 and the antigen recognized by PNA are different. After in vitro stimulation, the GL7(hi) B cell population has al so been found to be IgD negative. Functional comparison between in vitro ac tivated and MACS sorted GL7(hi) and GL7(lo/spleen) B cells of immunized mic e showed significantly higher specific and total antibody production as wel l as antigen presenting capacity in the GL7 hi population. (C) 2001 Elsevie r Science B.V. All rights reserved.