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‐1α 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‐1α 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.