Background: CD4(+)CD28(null) T cells are expanded in peripheral blood of patients with chronic kidney disease and associated with subclinical atherosclerosis. However, triggers for the oligoclonal expansion and activation of these cells are not clear.
Methods: We investigated twenty-five stage V-IV chronic kidney disease (CKD) patients and eight healthy subjects (HC). Peripheral mononuclear cells were isolated and incubated with heat shock protein- (HSP) 60 and 70. CD4(+)CD28(null) and CD4(+)CD28(+) cells were sorted by flowcytometry and antigen specific response was assessed by the mRNA and protein expression of interferon (IFN)-γ, perforin, and granzyme B using qRT-PCR and Elispot.
Results: The basal mRNA expression of IFN-γ, perforin, and granzyme B in CD4(+)CD28(null) cells was higher in subjects with CKD compared to that in HC (P < 0.0001). Subjects with CKD also showed expression of IFN-γ, perforin, and granzyme B in the CD4(+)CD28(+) subset, but this was much weaker than that seen in the CD4(+)CD28(null) population (P < 0.0001). We did not note the expression of these molecules at mRNA or protein level in either subset of CD4 cells in HC. After incubation with HSP60 and HSP70, CD4(+)CD28(null) cells showed increased expression at mRNA (P < 0.001) and protein level (P < 0.001). CD4(+)CD28(+) cells also showed a weak increase in expression. No antigen-specific response was noted in HC.
Conclusion: These data show that CD4(+)CD28(null) cells in subjects with CKD react with HSP60 and HSP70 by upregulating the expression of IFN-γ, perforin and granzyme B. Increased circulating level of HSP60 and HSP70 might play a role in initiation and/or progression of atherosclerosis in CKD subjects through perturbation of CD4(+)CD28(null) cells.