Analysis of the expression of the CD28 co-receptor revealed that high amounts of CD4+ T lymphocytes expressed this receptor, but in the GDM group (p < 0.0001) and the control group (p = 0.0092), less CD4+ CD28+ T cells were detected when PBMCs were stimulated with anti-CD3/anti-CD28 in relation to the culture with only a medium. The gene discussed is CD4; the disease is gestational diabetes.