Will a three-allele model of inheritance explain the HLA data for type 1 (insulin-dependent) diabetes?

The HLA data from nine published studies on Type 1 (insulin-dependent) diabetes were examined to see whether a three-allele model for the inheritance of Type 1 diabetes at the HLA-associated locus could be rejected. None of the data rejected the three-allele model. The data were also examined to see whether they would reject a recessive model. Out of the nine data sets, five rejected a recessive and four did not. The p value for all studies together rejected a recessive. Two of the data sets allowed us to test the hypothesis that multiplex and simplex families would exhibit different modes of inheritance. Multiplex data from both data sets rejected recessive inheritance while the multiplex data from only one data set also rejected three-allele inheritance. The results of assuming a recessive model and analyzing the data from simplex families led to different results from the two data sets. In addition, data from a non-European population were examined and found to reject both recessive and three-allele inheritance for Type 1 diabetes at the HLA-associated locus.