IgG subclass recognition pattern in leprosy: Recognition of M-leprae antigens by IgG1 and lgG3 antibodies is distinct across the disease spectrum

The recognition of Mycobacterium leprae antigens by IgG subclasses in patients with leprosy was investigated by electrophoresing M. leprae sonicate in SDS-polyacrylamide gel and immunoblot ting analysis. Serum pools were used from leprosy patients with either lepromatous (LL/BL) or tuberculoid (BT/TT) disease. A serum pool from healthy controls (EC) was used to determine the baseline antibody activity. To adjust for quantitative differences in antibodies across the disease spectrum, the LL/BL serum pool was used at a 1:200 dilution; the BT/TT serum pool, at 1:20 dilution. Monoclonal antibodies specific for each of the IgG subclasses were used as probes, with anti-mouse IgG conjugated to alkaline phosphatase as the revealing probe. Ige 1 antibodies bound to several discrete bands in the range of 10-70 kDa in LL/BL patients, while BT/TT patients showed a more diffuse pattern with the strongest IgG1 antibody binding in the region of 25-40 kDa. Recognition with IgG2 was restricted to a region between 25-36 kDa (which also stained strongly for carbohydrates) in both LL/BL and BT/TT patients. Binding with IgG3 antibodies was more restricted than IgG1 antibodies in LL/BL sera with strong recognition restricted to 25 and 25 kDa, BT/TT sera showed strong binding with IgG3 antibodies in the region of 25-32 as well as 5-7 kDa. IgG4 antibodies showed weak binding to a 28-kDa in lepromatous patients only. The differences in IgG subclass recognition patterns and their implications are discussed.