Figure 2.
Types of cell death seen in small intestine. (Reproduced with permission from Mayhew et al. [1999].) In type 1 cell death, a sequence of changes (1–4) leads to complete cells being extruded into the lumen. In type 2 cell death, only anucleate apical cell fragments are extruded. Two variants are distinguishable by the fate of the nucleated basal cell fragments. Type 2a cell death (sequence 1–3) creates large intercellular spaces extending from the apical fragment to the basal lamina and containing debris for phagocytosis. Type 2b cell death involves cell shrinkage and in situ degeneration of nucleated fragments in narrow intercellular spaces between adjacent enterocytes (sequence 1–4). The type 1 and type 2 cell deaths exhibit features of apoptosis. Type 3 cell death is reminiscent of necrosis. Cell swelling (1) and degradation (2–4) lead to breaks in epithelial continuity (open arrows), and end in spillage of degraded cell remnants into the lumen (2) or subtotal degradation and extrusion of a complete cell remnant (3–4). (LPM) Lamina propria macrophages; (IEL) intraepithelium lymphocytes.