On the afternoon of Dec 2nd 2021, Prof. Lilin Ye, a full professor in Army Medical University and Vice President of the Institute of Immunology of People's Liberation Army, was invited by Prof. Zhong Luo to give a talk entitled “Virus-specific CD4 T cell differentiation and immune memory” in LB101. The seminar was hosted by Prof. Zhengguo Li and attended by all faculties and students. The talk by Prof. Lilin Ye was based on his recent publications on Nature Immunology and Immunity, revolving around the critical roles of CD4 T cells in regulating the immune response of the host to invading viruses, especially the differentiation mechanism of Tfh and Tfr cells. After the seminar, Prof. Ye discussed a variety of topics with the faculties and students.