In both tumor and tumor-adjacent noncancerous tissues, higher stress was associated with decreased abundance of follicular helper T cells (tumor: β, −0.04 [95% CI, −0.08 to −0.0003]; P = .049; noncancerous tissue: β, −0.07 [95% CI, −0.11 to −0.03]; P = .002), a type of CD4 T cell associated with better breast cancer prognosis, and increased levels of immunosuppressive tumor-associated M2 macrophages (tumor: β, 0.04 [95% CI, −0.001 to 0.09]; P = .053). Here, CD4 is linked to breast cancer.