CD4 and breast cancer: In our study, we demonstrated that the increased infiltrated immune cells in RYR2-mutant BC were all antitumorigenic immune cells, and CD8 T cells were positively correlated with activated memory CD4 T cells and M1 macrophages, while CD8 T cells, activated memory CD4 T cells, and M1 macrophages were negatively correlated with protumorigenic M2 macrophages.