T-cell apoptosis in ICF syndrome

Detection of apoptosis by the TUNEL assay in CD4⁺ and CD4^– cells from patients with ICF. Each result is the percent of nuclei; dashed areas indicate normal nuclei, and black areas indicate apoptotic nuclei. n, Absolute number of nuclei counted for the area. Asterisk indicates statistically significant difference (P < .001).

Simultaneous detection of apoptosis by the TUNEL assay and of chromosomal rearrangements by FISH on interphase nuclei from freshly isolated lymphocytes of ICF patient 1. a, Chromosome 1qh hybridization signal with triradial configuration (arrow) in a partial metaphase. b, A similar triradial configuration is detected in an interphase nucleus subjected to FISH with the 1qh-specific probe pMG1; arrow indicates heterochromatic chromosome 1 hybridization signal, and arrowhead points to the hybridization signal of the normal chromosome 1. c, The same nucleus shown in Fig 2, b displays chromatin fragmentation, an early feature of apoptosis, as assessed by the TUNEL assay (bright green staining with FITC-dUTP). This finding demonstrates unambiguously that apoptosis affects a cytogenetically abnormal cell. d, Chromosome 1qh hybridization signal (pMG1 probe) of large size in an intertwined network of multibranched chromosomes (arrow) in a partial metaphase. e, In an interphase nucleus subjected to FISH with the pMG1 probe, the heterochromatic hybridization signal shows 2 large blocks joined by a thin stretch. This figure is the equivalent of the metaphase signal shown in Fig 2, d ; however, heterochromatin appears more decondensed, as expected in interphase. Arrowhead points to the hybridization signal of normal chromosome 1. f, The same nucleus shown in Fig 2, e displays chromatin fragmentation, an early feature of apoptosis (bright green staining with FITC-dUTP). The signals shown in red in Fig 2, e and in Fig 2, b appear here in yellow because of the use of the filter for FITC-dUTP detection, showing again that apoptosis affects a cytogenetically abnormal cell.