HLA antigens in Omanis with blinding trachoma: markers for disease susceptibility and resistance.

AIM: To determine the presence of HLA antigens in people with blinding trachoma. METHODS: Fifty Omanis with blinding trachoma were serologically typed for HLA A, B, C, DR, and DQ antigens and DNA typed for class II DR beta and DQ beta alleles and compared with a population of 100 healthy controls. RESULTS: chi 2 analysis of serological reactions did not reveal any significant differences in HLA antigen frequencies after correction of probability, although DR4, DR7, and DR53 were completely absent in the patients and all of the patients were HLA DQ1 positive. In the case of DQ1 the relative risk was 22.6 (95% confidence interval of 20.7-24.7). Class II DNA low resolution DR beta typing showed a significant increase in HLA DR16 (pc = 0.036, relative risk = 3.8) and a significant decrease in HLA DR53 (pc = 0.018, relative risk = 0.05). CONCLUSION: The finding that HLA DR16 (a DR2 subtype) is associated with susceptibility to blinding trachoma, a disease that is caused by an intracellular micro-organism, is consistent with reports of an HLA DR2 association with leprosy and tuberculosis, diseases also caused by an intracellular micro-organism. Similarly, resistance to leprosy is associated with HLA DR53 as is the case with blinding trachoma described here. It is postulated that HLA DR2 or subtypes in association with HLA DQ 1 may enable an intracellular micro-organism to enter the cell or are involved in presentation of peptides derived from intracellular micro-organisms to T lymphocytes initiating a delayed hypersensitivity or autoimmune reaction. These findings are the first report that genetic factors are of major importance in the development and protection against blinding trachoma.

Serological reactions to Nocardia antigens.

Sera from 23 patients with nocardiosis were tested for the presence of precipitating antibodies against an extract of Nocardia asteroides. Sera from nine of 20 patients infected with Nocardia asteroides and one of three sera from patients with Nocardia brasiliensis produced one to three precipitin lines with the antigen. Sera from eight of 55 patients with tuberculosis and 11 of 13 patients with leprosy also contained Nocardia precipitins. None of 33 sera from patients with cryptococcosis, blastomycosis, actinomycosis, histoplasmosis, coccidioidomycosis, mucormycosis or candidiasis contained Norcardia antibodies. None of the sera from ten patients infected with Staphylococcus aureus, ten patients infected with Pseudomonas, or 16 sera from uninfected patients contained Nocardia precipitins.