Insulin dependent diabetes mellitus susceptibility or protection may be determined by certain HLA-DQ molecules.

On the basis of our own studies and those of others, we suggest that several DQ molecules may be involved in IDDM susceptibility (Table 2). Our studies suggest that these DQ molecules may be encoded both when the DQA1 and DQB1 genes are in cis or trans position. A common denominator of several of these IDDM susceptibility molecules is that they have a non-Asp amino acid at DQ beta chain residue 57. Our studies demonstrate that this residue may be an important residue for peptide presentation to T cells.