Gliadin Antibodies in Adult Insulin-Dependent Diabetes - Autoimmune and Immunogenetic Correlates

Abstract

Gliadin antibody (GA) tests used in screening for coeliac disease (CD) frequently yield positive GA results without accompanying CD in cases of diabetes mellitus type 1 (DM-1). To enlighten this phenomenon we screened 848 DM-1 patients for IgA- and IgG-GA. Subsequently, 16 out of 19 high titre GA patients (6 with CD) were compared with 37 low titre DM-1 patients matched for sex, age and disease duration, for autoimmune and immunogenetic markers.

Chronic thyroiditis and thyroid peroxidase (TPO) antibody positivity were more frequent in the GA-positive than in the GA-negative sub-group (38 vs. 2.7%, p=0.003, and 69 vs. 27%, p<0.001, respectively).

The tissue transglutaminase (tTg) IgA titres correlated with CD but not with GA. tTg IgG titres were lower in GA-positive individuals (p = 0.0012). GA-positivity correlated with a higher titre of factor XIII IgA antibodies (p < 0.001).

GA-positive DM-1 patients were characterised by a distinct immunogenetic profile; the risk of HLA DQB1*02 was lower among GA-positive patients than among GA-negatives (OR 0.4, preventive fraction 0.43). All CD patients were HLA DRBl*03-DQBl*02-positive, but none of the five patients with normal biopsies. GA-positive patients instead had HLA DRB1 * 13 in 37.5% as compared to 8.6% in GA-negative (OR 6.4, etiologic fraction 0.32).

Thus, the occurrence of positive GA in DM-1 is correlated to TPO antibody positivity, thyroiditis and factor XIII IgA antibodies, but inversely correlated to tTg IgG, and seems to be associated with another HLA haplotype than that previously found to be associated with CD

Key Words:

• coeliac disease
• diabetes mellitus
• gliadin antibodies
• HLA
• thyroid disease