Circulating antibodies formed by?

Ans. is 'd' i.e., Plasma cells * Plasma cells are the antibody secreting cells. On contact with its appropriate antigen, the mature B cell undergoes clonal proliferation. The majority of activated B cells are transformed into plasma cells and secrete antibodies* While plasma cell is the best antibody producing cell, lymphocytes, lymphoblasts and transitional cells may also synthesise Ig to some extent