Immune-related genes (IRGs) affect the composition and abundance of tumor-infiltrating immune cells (TIICs) by encoding immune molecules. The utilization of IRGs and TIICs offers considerable potential for immunotherapy studies of breast cancer. In this study, the differentially expressed genes (DEGs) between breast cancer patients and healthy individuals were assessed using the Cancer Genome Atlas (TCGA). ImmPort and TISIDB databases, the Weighted Gene Co-Expression Network Analysis (WGCNA), univariate Cox regression and LASSO penalized Cox regression methods were used to calculate the composition and abundance of immune cell types. It was found that CD79A and GZMAcould independently predict the prognosis of breast cancer and were significantly associated with activated CD8 T cells, immature B cells, folic helper T cells and regulatory T cells, implying that these two genes are involved in the immune regulation and progression of breast cancer and could potentially be new targets for breast cancer immunotherapy.