CD24 and osteoporosis: A previous study reported a positive correlation between altered memory B lymphocytes and both FN- and LS-BMD in women with osteoporosis (18), which was inconsistent with our reported results of mediation analyses, in which there were negative causal relationships between the total effect of several memory B cells (e.g., early Bm5 and late Bm5 memory cell) with BMD and a negative effect of CD24 on memory B cell on BMD in MR analyses.