Sensitivity and nonspeicific staining of various immunoperoxidase techniques

Optimally fixed paraffin enbedded tissue sections and cytocentrifuged cell smears were used to test the sensitivity and nonspecific staining with the enzyme-bridge, PAP, indirect and direct immunoperoxidase methods using human immunoglobulins and lysozyme as antigens. With the enzyme-bridge method positive staining was seen with primary antiserum dilutions up to 1:20,000. The least background staining was observed with this method. The PAP method was equally sensitive, although false-negative results with low primary antiserum dilutions were seen. Some nonspecific background staining always persisted using the PAP method even with high primary antiserum dilutions. The indirect method was not as sensitive as the enzyme-bridge method and some nonspecific staining always persisted. The direct method was too insensitive with paraffin embedded tissue sections.