Fig. (1) Recognition of HPV-16 E7 protein by monoclonal and polyclonal antibodies. (A) HaCaT (H) and CaSki (C) cells were labeled with [³⁵S]-methionine-cysteine and immunoprecipitated with different anti-E7 polyclonal (C24, C89) and mAbs (G7, B4, C2, D11, C20, A5, ED17). The arrows show a 16 kDa band recognized by all antibodies, and a 17 kDa band detected only by polyclonal antibodies. (B) Cell extracts were first immunoprecipitated with the C24 polyclonal antibody, samples treated for Western blot and tested with polyclonal and mAbs. The arrow shows the E7 protein of 16 kDa.