Detection of MLH1 and MSH2 proteins using combined MLH1 and MSH2 monoclonal antibodies on the same blot. (A) HCT116 and LoVo cells were used as controls for the absence and presence of MLH1 and MSH2 proteins, respectively, whereas SW480 cells were used for the presence of both these proteins. There was no apparent cross-reactivity. (B) Different concentrations of SW480 cell extracts were used for western blotting to establish simultaneous detection of both proteins. Results indicated that the combined antibodies were able to specifically detect their respective antigens in a dose dependent manner. MLH1 and MSH2 proteins could be detected in samples containing as little as 10 ug of total cell protein. (C) Detection of MLH1 and MSH2 proteins on western blots with a mixture of varying amounts of HCT116 and LoVo cell lysates. Results show that the combinations of these two monoclonal antibodies were able to detect MLH1 and MSH2 proteins even when these proteins were present in a sample in different proportions.