Primary immunodeficiency is mainly caused by abnormal development, differentiation and function of immune cells. Studies have shown that epigenetic regulation plays an important role in the development of immune cells. The study found that histone methyltransferase Nsd2 plays an important role in the regulation of B cell development, and found an important pathway regulating B cell development by transcriptome sequencing. This study provides a new therapeutic target for the treatment of primary immunodeficiency diseases.。