EXISTENCE OF LOW-MOLECULAR-WEIGHT IMMUNOGLOBULIN-M IN CARP EGGS

Immunoglobulin in the eggs of carp was analyzed by SDS-polyacrylamide gel electrophoresis and Western blotting, using affinity purified anti bodies against carp immunoglobulin M (IgM). Carp eggs were confirmed t o contain IgM. However, gel filtration patterns revealed that egg IgM was of notably lower molecular weight than plasma IgM. Therefore, the egg IgM was considered not to be a tetramer, although the exact molecu lar weight could not be determined. Moreover the molecular weight of t he heavy chain of egg IgM (68 kDa) was smaller than that of plasma IgM (75 kDa). Differences in IgM molecular weight may be due in part to t he differences in the polypeptide composition of the heavy chain. The presence of egg type IgM was clearly demonstrated in the mature ovary, and was also faintly detected in immature ovaries possessing early yo lk globule stage oocytes. These observations suggest that the accumula tion of IgM occurs in conjunction with the accumulation of vitellogeni n in the oocytes.