As a negative control, the primary antibody was omitted from the reaction.

Detection of this first or primary antibody can be accomplished in multiple ways.

A sample is treated with a primary antibody specific for the molecule of interest.

The higher the concentration of the primary antibody present in the serum, the stronger the color change.

Pursuant to this indirect method, the primary antibody is added to the test system.

Primary antibodies were diluted in blocking solution and applied for 1-2 hours.

We also tested the specificity of primary antibodies in western blots.

With the direct method, it would be necessary to label each primary antibody for every antigen of interest.

Slides were incubated at room temperature for 1 h with the primary antibodies.

A fluorophore can be directly conjugated to the primary antibody.