CD28 and chronic kidney disease: Although the effect of ESRD on the expression of the CD28 molecule was proven, and many investigators agree that patients on chronic kidney disease stages IV–V show a significant increase in the frequency of CD4+CD28null cells, the further effect of dialysis is controversial, with some investigators finding no differences between predialysis and dialysis-dependent ESRD patients, and others showing CD28null cells further expanding in patients on HD [10,35,36].