Expression and function of DNAM‐1 on human B‐lineage cells

Abstract

Background

Although DNAM‐1 is an activating receptor constitutively expressed on the majority of NK cells, CD8⁺ T cells, CD4⁺ T cells, monocytes, and platelets in human, several evidences demonstrated that a small population in B‐lineage cells also expressed DNAM‐1. However, the expression profile of DNAM‐1 on B‐lineage cells and its function remain obscure. Previous reports revealed that a considerable number of leukocytes including B cells in the peripheral blood conjugated to platelet. Thus, the proportion of DNAM‐1⁺ B‐lineage cells determined by flow cytometry analysis in the previous reports might be overestimated.

Methods

We examined whether platelets conjugate B cells and then analyzed the expression of DNAM‐1 on the subpopulations of B‐lineage cells according to their maturation stages after exclusion of platelet‐conjugated B cells. We also assessed the involvement of DNAM‐1 in IL‐10 and antibody production from cultured B‐lineage cells stimulated with CpG‐ODN.

Results

Approximately 10% of human DNAM‐1⁺ CD19⁺ B cells in the peripheral blood conjugated to platelets, resulting in the overestimation of the proportion of DNAM‐1⁺ B cells. After exclusion of platelet‐conjugating B cells, we show that DNAM‐1 expression was detected on subpopulations of memory B cells, plasmablasts, and plasma cells and upregulated by stimulation with CpG‐ODN. Moreover, DNAM‐1 was involved in IL‐10 and antibody productions by B cells after CpG‐ODN stimulation.

Conclusions

DNAM‐1 may be involved in B‐lineage cell‐mediated immune responses.