Abstract: Objective To study the expression of inhibitory receptor LAIR-1 on the megakaryocytic lineage cells and the regulatory effect of LAIR-1 on the differentiation of megakaryocytes (MKs). Methods Flow cytometry (FCM) and laser confocal technique were used to detect the expression of LAIR-1 on the megakaryocytic lineage cells. Cord blood CD34+ cells were purified by a positive selection using an immunomagnetic separation system. The CD34+ cells were induced to differentiate to MKs by serum-free medium system in vitro. LAIR-1 was activated by cross-linking with antibody or ligand and then the effect of LAIR-1 on the differentiation of MKs was detected. Results LAIR-1 was expressed on the surface of CD34+CD41a+ and CD41a+CD42b+ cells in the bone marrow of human. In human cord blood, the surface expression of LAIR-1 is detectable in CD34+CD41a- and CD34+CD41a+ cells. When cord blood CD34+ cells were induced to megakaryocytic differentiation, LAIR-1 presented in immature CD41a+ cells with cell ploidy of 2N and 4N. Cross-linking of LAIR-1 appeared to inhibit the differentiation of MKs from cord blood CD34+ cells. Conclusion LAIR-1 may be a new negative regulatory molecule participating in the early-stage differentiation of MKs.

Key words: LAIR-1, megakaryocyte, bone marrow, cord blood