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Immunoperoxidase Studies of a Normal Node

L26 (CD20), a pan-B-cell marker. Anti-CD20 antibodies have adhered to B-cell membranes and reacted with a chromogen to leave a brown residue on them. Thus they have marked in brown the reactive follicles, where the B-cells are proliferating.

CD3, a pan-T-cell marker. It has marked mostly the paracortical T-cells surrounding the follicles.

A light chain stain (at much higher power than the other photomicrographs on this page). In paraffin embedded tissue, antibodies for light chains react almost exclusively with cytoplasmic (as opposed to membrane) immunoglobulin light chains. Here anti-kappa antibodies have picked out the plasma cells with kappa light chains in their cytoplasm. To detect membrane light chains, it would be necessary to use frozen tissue as a substrate for immunoperoxidase studies (or use a different technique, like flow cytometry).

CD68: this antigen is seen on most histiocytes (also known as macrophages). Here it has picked out the tingible-body macrophages within a reactive follicle.

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