The Frequency of HLA Alleles in Korean Children with Aplastic Anemia and the Correlation with the Response to Immunosuppressive Treatment

Kook, Hoon; Hwang, Tai Ju; Seo, Jong Jin; Ghim, Thad T; Moon, Hyung Nam; Lee, Young Ho; Kim, Moon Kyu; Lee, Kun Soo; Lee, Kwang Chul; Hwang, Pyoung Han; Park, Hyun Jin; Park, Kyung Duk; Park, Jae Sun; Shin, Hee Young; Ahn, Hyo Seop

Abstract

PURPOSE
Immune pathophysiology of aplastic anemia (AA) has been indirectly inferred from responses to immunosuppressive agents. An association between AA and HLA-A2, or HLA-DR2 (its serologic split, HLA-DR15; or its molecular correspondents, DRB1*1501) has been implicated. The presence of HLA-DR15 (including DR2 or DRB1*15) has been closely associated with a favorable response to immunosuppression in AA. This study was aimed to characterize Korean patients with AA by determining the association with certain HLA alleles, such as HLA-DR2 or HLA-A2, and their implications in terms of the response to immunosuppression. METHODS: One-hundred eighteen children with AA from 10 university hospitals between 1990 and 2001 were enrolled in this multicenter, retrospective study. Among them, HLA data were available from 80 patients. Tests of proportions were used to compare allelic frequencies. RESULTS: The frequency of HLA-A2 (58.8%) or HLA-DR2 (24.7%) in AA was not significantly different from those of the controls. Analysis of the patients treated with immunosuppression (N=86) showed that, 50.0% of patients showed a response, including 16.0% of complete response at 6 months. The presence of DR2 allele did not portend a favorable response to immunosuppressive therapy. CONCLUSION: Unlike Western countries, the association of AA with certain HLA alleles was not documented in the Korean population. Moreover, the presence of HLA-DR2 did not predict a favorable response to immunosuppression. This peculiar characteristics of Korean AA needs to be investigated whether these findings reflect ethnic differences, different contribution of immune-mediated AA, different immune mechanisms, or mere limitation by number of study patients.