The effect of cyclophosphamide on B cells in spleen (rat)

Stain: Immunofluorescence of Vector red using Mark-1 antibody against B cells. A: Normal rat spleen. (1) the dark, unstained area represents the PALS (periarteriolar lymphatic sheath) filled with T cells. (2) red-stained germinal centre of a B cell follicle that is surrounded by the marginal zone (3). Note that B cells are also distributed in the red pulp area (4). B: 4 days after a single treatment with cyclophosphamide the number of red-stained B cells are considerably reduced in the follicles (2) and marginal zones (3), but also in the red pulp (4). The cyclophosphamide treatment causes a temporarily severe reduction of the immune response to antigens, partly to the reduced levels of B cells.