Retroviral vector expression in TCR transgenic CD4⁺ T cells.

The regulation of gene expression is key to understand the function of genes of interest. To explore the biological functions of genes, transgenic knock-in or knockout technologies have served as invaluable tools. While recent advances in molecular biology have introduced new techniques (i.e., CRISPR mediated gene editing) (Cong et al., Science 339(6121):819-823, 2013; Wang et al., Cell 153(4):910-918, 2013) for the generation of transgenic mice in a relatively short period of time, it can still take a long time to test biological hypotheses from scratch to design how to generate knock-in or knockout mice. Here, we describe methods to manipulate gene expression in T cell receptor (TCR) transgenic CD4 T cells, which allow us to investigate gene functions in the study of differentiation pathways of follicular helper T (Tfh) cells.