Although the expression of CD28 and ICOS was unaltered in AD patients at the point in time of diagnosis, a stage-dependent analysis showed that the expression of CD28 on CD4 + T cells decreased from mean 44.8% in non-demented controls to 35.2% in patients with severe AD (p = 0.0270; Fig. 2a). The gene discussed is ICOS; the disease is Alzheimer disease.