CCL19 and infection: Moreover, it has also been found that although Trm cells are resistant to HIV compared with activated CD4+T cells, mild stimulation of chemokine CC ligand 19 (CCL19) and chemokine CC ligand 21 (CCL21) and cytokines interleukin (IL)-4 and interleukin (IL)-7 can promote the direct infection of resting CD4+T cells with HIV without inducing significant T cell activation (Saleh et al., 2007; Wu, 2010; López-Huertas et al., 2019).