In situ expression of recombination-activating genes in human tonsil.
In situ hybridization reveals focal clusters of RAG-positive cells in human tonsil sections as indicated by the presence of black silver grains. (A) Low power magnification shows tonsillar epithelium at the right margin of this figure. The boxed area is shown at high power in B and C. (B) Using 35S-labeled RAG-specific antisense probes, several labeled cells are detected in this area, whereas in (C) no specific labeling is seen in the same area using the corresponding sense probes. (D) In a different tonsil, numerous RAG-expressing cells are seen at the boundary between lymphoid tissue and fibrous connective tissue. (E) A higher power view of the same areas as in D. (F) In another tonsil, RAG-positive cells are observed in the vicinity of a germinal center (GC). (G) A high power view of the same area as in F. (H) No specific labeling is seen in the same case using the corresponding sense probes.
