Purification and molecular characterization of IgM in olive barb, Puntius Sarana

In the present article, immunoglobulin (Ig) of Puntius sarana (a vulnerable medium carp species) was purified by affinity chromatography, characterized, and identified as only IgM type with a native molecular weight of 879 kDa having one heavy (88 kDa) and one light (26 kDa) chain. Further, the developed rabbit antisera against IgM was found to be quite specific to P. sarana IgM and used in ELISA to measure the antibody titer in P. sarana at different time periods, against an antigen (hemocyanin) injection with and without adjuvant. The antibody titer was significantly higher in most of the time periods in both groups, however, the adjuvant-treated group showed higher antibody titer at days 43 and 90, compared to non adjuvant-treated group. Further, the partial IgM sequence was amplified and its expression level was checked during ontogenesis. The IgM transcript was detected from unfertilized egg stage to 4 days post fertilization (dpf) and again reappeared at 21 dpf whereas during infection with Aeromonas hydrophila, significantly marked up-regulation of the gene was observed at 12 hr, 24 hr, and 7 days post-infection time periods indicating the role of IgM during early embryonic time period as well as during bacterial pathogenesis.