Apoptosis in gut-associated lymphoid tissue (GALT)

概要

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Gut-associated lymphoid tissue (GALT) consists of germinal centers (GCs) and interfollicular areas (T-cell-dependent areas). In GCs, B cells undergo apoptosis as a result of failure to perform affinity maturation. Recent studies indicated that DNA is not cleaved in the condensed chromatin of lymphocytes in the thymus. Thus, DNA fragmentation occurs after lymphocytes are phagocytosed by macrophages. The aim of this study is to demonstrate the occurrence of DNA fragmentation during apoptosis in GALT. Fas or Fas-ligand-positive cells were found to be localized in GCs. TUNEL-positive cells were found to be mainly localized in the cytoplasm of macrophages. However, caspase 3 activity was detected in GALT, immunoreactivity of caspase 3 was in the F4/80 (a marker for macrophages) positive cells. In conclusion, the unselected B cells undergo apoptosis by the Fas/Fas ligand system, and then they are phogocytosed by macrophages before their DNAs are fragmented. DNA fragmentation in these cells occurs via the caspase 3-dependent cascade when these cells are engulfed by the macrophages.
日本組織細胞化学会の論文