I am getting a high background in the negative control (Normal secondary IgG) lane. The protocol is the lysate (about 500ug) is mixed with capture antibody and negative antibody overnight at 4C. Next day the Protein A/G beads are incubated for 2 hrs. The mix is washed with lysis buffer (NP-40 without PI/PMSF), boiled and the supernatant is loaded on the gel, transferred on NC membrane, blocked in Nonfat dry milk for about 2 hrs at RT, and incubate the membrane with detection antibody O/N, secondary antibody for about 1.5 hrs and develop with ECL.Capture antibody and detection antibody are of the same species.

How to reduce the background in negative IgG lane which shows smearing from heavy chain band (50 kda ) until the light chain band (25kda)?