True about IgM: (A) Fix Complement, (B) Increased in primary response, (C) Fab region is composed of variable region, (D) Fc is antibody - binding option
Answer is A. IgM Produced in the primary response to an antigen Fixes complement.Does not cross the placentaAntigen receptors are on the surface of B cells.IgG is also involved in complement fixationReference: Harper biochemistry 30th edition page no 681