Diabetes, Vol 43, Issue 1 110-117, Copyright © 1994 by American Diabetes Association
Major histocompatibility complex-encoded antigen processing gene polymorphism in IDDM
PM van Endert, RS Liblau, SD Patel, L Fugger, T Lopez, F Pociot, J Nerup and HO McDevitt
Department of Microbiology, Stanford University School of Medicine, CA 94305-5402.
Susceptibility to insulin-dependent diabetes mellitus (IDDM) is greatly
influenced by polymorphisms in the genes of the class II region of the
human leukocyte antigen (HLA) complex. The complexity of this genetic
association and the lack of a direct proof of involvement of HLA class II
genes in human IDDM have continued to support speculation on a possible
role of genes encoded in the close vicinity of these loci in IDDM. Because
the recently discovered transporter associated with antigen processing
(TAP) and large multifunctional protease (LMP) genes are encoded in the HLA
class II region and are implicated in the processing of antigenic proteins
for presentation by HLA class I molecules, they are additional candidates
for a role in IDDM pathogenesis. We have analyzed genomic and coding
sequence polymorphisms in the LMP2, TAP1, and TAP2 genes of 77 Danish IDDM
patients and 102 control subjects. Although patients and control subjects
did not differ in TAP1 and LMP2 alleles, we found a striking absence of the
TAP2 allele B (long form) in IDDM patients. An analysis of the TAP2 alleles
in individual DR types, however, revealed that this phenomenon is likely to
be caused by linkage disequilibrium between the two loci. Thus,
polymorphisms in the TAP and LMP genes are unlikely to be associated with
IDDM.