Chemokine expression during acute rejection of rat kidneys

During acute rejection of fully allogeneic rat renal allografts, few neutrophil granulocytes are detected, whereas an abundant infiltrate of macrophages and T lymphocytes becomes apparent. The mechanisms leading to this specific pattern of infiltration are not understood. We performed a sequential daily Northern blot analysis of the mRNA expression of the CC-chemokines MCP-1, MIP-1alpha and RANTES and of the CXC-chemokines GRO/KC and MIP-2 in rat renal isografts (LEW --> LEW, n = 1 per day) and allografts during acute rejection (DA --> LEW, n = 3 per day). MCP-1 gene expression strongly increased on days 3-4 after allotransplantation and returned to control levels on day 6. The expression of MIP-1alpha and RANTES continuously rose until day 3-4 and remained stable thereafter. Isografts displayed minor changes in CC-chemokine expression. In contrast to CC-chemokines, GRO/KC was expressed in low amounts during rejection and MIP-2 mRNA remained undetectable. In conclusion, the expression of the CC-chemokines MCP-1, MIP-1 and RANTES was clearly upregulated during rejection, whereas the mRNA of the CXC-chemokines MIP-2 and GRO/KC was not detected at all or remained at low levels. This pattern of chemokine gene expression is in good accordance with the predominant mononuclear leukocyte infiltrate in allografts.