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.