We reported previously the
autoantibodies directed to
caspase-8 among patients with
silicosis,
systemic sclerosis (SSc) and
systemic lupus erythematosus (SLE) , and in healthy individuals. In this study, we analyzed the correlation between anti-caspase-8
autoantibody responses and HLA class II alleles in
silicosis patients. The frequencies of
HLA-DRB1*0406 were significantly higher in antibody positive patients (16.67%) than in control individuals (3.03%, p=0.0006). The
lysine (K) at position 71 as in DRB1*0406 has been reported to be associated with
rheumatoid arthritis (RA) and
insulin dependent diabetes mellitus (
IDDM). The haplotype HLA-DR4; DQB1*0302 was detected in 4 of 12 antibody positive patients. RA,
IDDM, or pemphygus vulgaris link to the haplotype. The frequencies of DQB1*0401 were significantly lower in antibody positive patients (0%) than that in controls (13.33%, p=0.0390). The
aspartic acid at position 57 in the DQB1 molecule as in DQB1*0401 is reported to play a role in the resistance to
IDDM. The frequency of DPB1*0601 in antibody positive patients (5.88%) was significantly higher than that in controls (0.56%, p=0.0003). DPB1*0601 is reported to be a risk factor among RA patients, and
glutamate at position 69 of the DPB1 molecule may be involved. Repeated and continuous screening of
autoantibodies seems to be necessary among workers in contact with Si-related substances for the detection of immunological disorders in the early stage.