40.2.2 Immunofluorescence and immunohistochemistry

Antibodies can be used to visualize the presence of antigen within the cell and tissue. A conventional way to localize the antibody is by immunoperoxidase technique using horseradish peroxidase or alkaline phosphatase. In immunofluorescence the fluorescence labeled antibody is incubated with the cells or tissue and are visualized under the immunofluorescence microscope. More advanced version of the immunofluorescence microscope is confocal microscopy where details of the cells can be visualized by more sophisticated laser technology.

40.3 Studying T cell response

T cell activation depends on the stimuli or the external antigen presented to it through an antigen presenting cell. Many carbohydrate binding lectins such as concanavalin-A and phytohemagglutinin are used to activate T cell as a polyclonal activator . Polyclonal activation is done in order to activate the T cells against an unknown antigen. T cells can also be activated by pharmacological reagents such as phorbol ester and ionophores. This method is useful in studying the antigen activated T cells that are previously primed with a different antigen.

40.4 Studying B cell response

Polyclonal activation of B cell is difficult as only few cells are specific against an antigen during the time of clonal selection. Generally anti-Ig antibodies are used for polyclonal activation of B lymphocytes. Anti-Ig antibodies bind to the constant region of the membrane bound Ig on the B cell which will have the same effect as of the antigen binding to the hypervariable region of the Ig.