This invention is directed to a method for preparation of a biological sample for measurement of
protein epitopes that allows for the preservation of
intracellular protein epitopes and detection of
signal transduction pathways based on the ability to capture transient activation states of the epitopes. The method provided by the invention allows for the rapid fixation of biological samples containing red blood cells, to ensure that epitopes of
signal transduction molecules and other
intracellular protein epitopes are preserved in the
active state. The method of the invention further allows for
lysis of red blood cells, thereby making it a useful method for cytometric analysis of biological samples, including, for example,
whole blood,
bone marrow aspirates, peritoneal fluids, and other
red blood cell containing samples. The invention also provides a method to recover or “unmask” epitopes on
intracellular antigens that have been made inaccessible by the cross linking fixative necessary to fix the sample. Significantly, the methods of the invention allow preservation and analysis of phospho-
epitope levels in biological samples taken directly from patients to determine
disease-specific characteristics.