Japanese Society for Histocompatibility and Immunogenetics (JSHI) has a certification system for HLA technologist and Director for Histocompatibility testing, in which ability and knowledge about the histocompatibility and Immunogenetics is required. To evaluate the ability and knowledge, a paper examination is obliged. Here I will comment on several questions of which percentage of correct answer was below 40% in the last year 2017.

A number of HLA alleles have been reported to be associated with various traits such as autoimmune diseases, infectious diseases, and adverse drug reaction in case-control association studies. Since there are many alleles at classical class I and class II HLA loci, a stringent significance level as corrected by the Bonferron method has been used in the statistical hypothesis testing to reduce false positives. However, the Bonferroni correction is too conservative to detect HLA alleles showing weak association, and thus many false negatives seem to have occurred in HLA-disease association studies. Here, I describe a chi-square test based on 2 by 2 contingency table for evaluating the association of each HLA allele at the locus with a dichotomous trait such as disease. In addition, I review the adjustment of significance level in association tests for loci with many alleles.

The chances to use HLA-mismatched related or unrelated donor candidates are rapidly increasing in cases wherein HLA-matched related or unrelated donor candidates are unavailable or immediate transplantation is required for disease control. Since the counting methods of HLA matching and the effect of HLA matching on transplant outcomes differ according to stem cell sources, the effects of HLA mismatch should be cautiously interpreted. The HLA locus, matching level (antigen or allele), and mismatch direction (graft-versus-host or host-versus-graft direction) must be understood. The effect of HLA mismatch on transplant outcomes has been assessed by many studies; however, it must be recognized that it is changing with improvements in graft-versus-host disease prophylaxis. In this issue, the effect of HLA mismatch across various stem cell sources is discussed.