vIL-6 and ORF45 in KSHV-MCD Patients. (A) LANA expression in a germinal center involved with KSHV-MCD. LANA, stained in brown with DAB, appears as nuclear speckles in KSHV-infected cell nuclei. The majority of LANA-expressing plasmablasts are in the mantle zone. (B) vIL-6 expression in an adjacent cut from the same germinal center. There were fewer vIL-6-expressing cells, and these were less focused in the mantle zone. (C and D) ORF45 and vIL-6 coexpression in a germinal center involved with KSHV-MCD. ORF45 (a KSHV lytic gene) was stained in brown, while vIL-6 was stained in red. Panel C shows the whole germinal center while panel D shows a section at higher magnification. ORF45 and vIL-6 are colocalized in many cells (solid arrows). Some cells express only vIL-6 and not ORF45 (dashed arrows). (E) ORF45 and vIL-6 expression in a KSHV-MCD lymph node observed by IF and confocal microscopy. Each horizontal row shows a separate field from the same section in one of two patients examined. ORF45 was stained in red, and vIL-6 was stained in green. Some cells expressed only vIL-6 and not ORF45.