CELLULAR INTERNET IN THE GERMINAL CENTER 113 FIGURE Immunofluorescence co-localization of (A) Cx43 gap junctions and (B) desmosomal junctions (desmoplakin reaction) in a human tonsil section. Note the same distribution of both types of junction with strong expression in the germinal center (GC; right half of the images) and gradual downregulation toward the paracortex (PC; left half of the images). Bar: 20 #m. FIGURE 2 Simultaneous immunofluorescence for (A) Cx43 and (B) Ki-67 antigen in a tonsillar germinal center. Cx43 gap junctions are concentrated in the light zone (A; LZ), where B centrocytes are hardly labeled for the proliferation marker antigen Ki-67 (B). There are only few junctions in the dark zone (DZ) full of proliferating centroblasts. Bar: 20/m.