Genetic variations at the T cell receptor gamma locus in circulating peripheral blood mononuclear cells of clinically categorised leprosy patients.
The allelic polymorphisms at exon 3 and exon 2 of the T cell receptor (TCR) C gamma 2 (TRGC2) gene, generating 18-kb and 5.4-kb HindIII fragments, respectively, were found to be more frequent in multibacillary leprosy patients than in the controls (P < 0.005 and P < 0.001, respectively) when screened with the IDP2.11 probe. The frequencies of heterozygotes for the 18-kb allele and homozygotes for the 5.4-kb allele were found to be significantly higher in the multibacillary patients than in the controls (P < 0.001). Interestingly, the 8.0-kb allele, originating from the triplication of exon 2 of C gamma 2, was observed exclusively in the paucibacillary leprosy patients. Further, when DNA samples were screened with the pH60 probe for the HindIII RFLP at the TCR J gamma 2 (TRGJ2) gene segment, the 2.1-kb allele was again more prevalent in leprosy patients with the multibacillary form of the disease than in the paucibacillary patients and the controls (P < 0.025). The frequency of homozygotes for the 2.1-kb allele was also significantly higher in the multibacillary patients than in the paucibacillary patients (P < 0.010) and the controls (P < 0.025). A significant difference was observed in the frequencies of detectable rearrangements involving the V gamma 7/8 and V gamma 9 gene segments at the gamma locus between circulating peripheral blood mononuclear cells of the multibacillary leprosy patients and the controls. These rearrangements were detected less frequently in the multibacillary patients (P < 0.001 for V gamma 7/8 and P < 0.005 for V gamma 9).