Recent evidence from our laboratories and from others has suggested the ability of monoclonal antibodies (MAb) against a human B lymphocyte alloantigen to discriminate between RF/RHD susceptible individuals and persons with a lower risk of developing RF. However, while such MAb can identify a majority of RF/RHD patients in some populations, reduced discriminatory ability has been observed in other groups. Antigenic variation in the marker(s) may exist among ethnic groups which can adversely influence the specificity of the test. To examine this possibility, we developed MAb made from B lymphocytes of North Indian ethnic origin. In the same population we compared a new MAb (PGI/MN II) with a previously described MAb of Caucasian ethnic origin (D8/17). The results indicate significantly (p<0.0001) greater discriminating ability of this new MAb for patients with RF/RHD in the North Indian population and support our hypothesis.

MAb were made by standard techniques with peripheral blood B lymphocytes from a well-documented RHD patient from Haryana state in northern India. The new MAb (PGI/MN II) was compared with D8/17 in the same Indian population using flow cytometry and/or immuno-histostaining techniques in ARF patients(no previous evidence of RF) who fulfilled the Jones Criteria, patients with documented chronic RHD and with appropriate normal controls from the same population. Further, 142 siblings of the RF/RHD patients were also evaluated.(As previously described, subjects were considered positive when >10% lymphocytes reacted with a MAb.) Table 60% of the siblings of the RF/RHD patients were positive when tested with PGI/MN II.

Table 1

Our data demonstrate an enhanced discriminating ability of PGI/MN/II to identify ethnic Indian RF/RHD patients when compared with the MAb of Caucasian origin. Additionally, our evaluation of siblings of RF/RHD patients suggests an apparent higher risk in these blood relatives. These data also strongly suggest that before such MAb can be used in public health programs for RF detection and prevention, variation among different ethnic populations must be carefully evaluated and defined.