CD28 and diabetes mellitus: mRNA expression of the activated lymphocytes showed that diabetes impaired the Akt1 (234 ± 9.5), CD28 (229 ± 14) and Cdc42 (33 ± 6.5) signaling compared to those of the control group [Akt1 (252 ± 12), CD28 (235 ± 10), Cdc42 (45 ± 5.0)].