A method of activating an antigen is herein described. The method comprises providing an antigen activation solution and contacting the cell with the solution to activate the antigen. A method of detecting a cell fixed by a nonbridging fixation solution is also described. The method comprises providing an antigen activation solution, contacting the cell with the solution, immunostaining the cell, and detecting the stained cell. The solution used for these methods comprises an agent for breaking a hydrogen bond, and is also described herein.