CD4 and breast cancer: In a small group of patients, we observed that those with metastatic HER2 + breast cancer and high serum levels of miR-19a-3p (indicating a good prognosis) exhibited a trend of higher levels of activated CD4 + T cells secreting IL-2 and IFN-γ, as well as NK cells, in their blood compared to patients with low levels of miR-19a-3p (indicating a poor prognosis).