Background: The major histocompatibility complex class I chain-related gene A (MICA) is located in MHC class I region near HLA-B. MICA is one of the polymorphic non-HLA antigens important in kidney transplantation. The information on the distribution of MICA alleles and antibodies in Thai kidney transplant recipients is still lacking.

Objective: To determine MICA allele frequencies, their linkage with HLA-B and MICA antibody frequencies in Thai kidney transplant recipients.

Materials and Methods: One hundred thirty Thai kidney transplant recipients were typed for MICA by PCR-SSP and HLA-B by microlymphocytoxicity. There were 484 recipients tested for MICA antibody screening by LABScreen Mixed and for MICA antibody specificities by MICA single antigen kit. Allele frequencies of MICA, linkage disequilibrium with HLA-B and antibody frequencies of MICA were analyzed.

Results: The four most frequent MICA alleles were MICA*008, *019, *010, *002. The most frequent MICA-HLA-B haplotypes were MICA*010-B46, MICA*008-B60, MICA*019-B75, MICA*018-B18. The most frequent specific antibodies were MICA*007, *002, *001.

Conclusion: The polymorphism of MICA gene and strong linkage disequilibrium with HLA-B were found in Thai kidney transplant recipients similar to the healthy Thais. The specificities of MICA antibodies did not correlate with MICA alleles.

Keywords: MICA, Transplant, Thai