A new natural anti-alpha-galactosyl IgG antibody (anti-Gal) was found to be present in high titer in the serum of every normal individual studied. The antibody was isolated by affinity chromatography on a melibiose-Sepharose column. The reactivity of the antibody was assessed by its interaction with alpha-galactosyl residues on rabbit erythrocytes (RabRBC). The specificity was determined by inhibition experiments with various carbohydrates. The anti-Gal interacts with alpha-galactosyl residues, possibly on glycolipids of human RBC (HuRBC), after removal of membrane proteins by treatment with pronase. In addition, the anti-Gal bind specifically to normal and pathologically senescent HuRBC, suggesting a physiological role for this natural antibody in the aging of RBC. The ubiquitous presence of anti-Gal in high titers throughout life implies a constant antigenic stimulation. In addition to the theoretical interest in the antibody, the study of the anti-Gal reactivity seems to bear immunodiagnostic significance. Decrease in the antibody titer was found to reflect humoral immunodeficiency disorders.

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During the last decade the frequency of therapy-related acute leukemia (t-leuk) and myelodysplastic syndrome (t-MDS) has been increasingly observed. Over the past 15 years, we treated 56 patients with t-leuk who had received prior chemotherapy (39%), radiotherapy (11%), or both (45%). The drugs received included alkylating agents and topoisomerase II inhibitors. The primary tumors included hematological malignancies (49%) and solid tumors such as breast or ovarian cancer. The median age at diagnosis of the primary tumor was relatively young (43 years +/- 18). Twelve patients had more than one primary tumor and 31 patients had a family history of malignancy. Karyotypic abnormalities were found in 91% of the patients. Prognosis was uniformly poor, with an overall median survival of 10 months. Twelve of the 18 patients examined (67%) had a multidrug resistance phenotype. P53 genes of the leukemic cells, as well as the original tumors, were analyzed in 21 patients using polymerase chain reaction (PCR) with single-stranded conformation polymorphism analysis followed by sequencing. P53 mutations were identified in 38% of these patients, a relatively high prevalence compared with other forms of MDS or de novo acute myeloid leukemia. Mutations were nongermline and restricted to the leukemic cells. We identified different p53 mutations in the various primary tumors of individual patients. The presence of a mutator phenotype was assessed by PCR analysis of microsatellites in eight loci (one trinucleotide repeat sequence, four dinucleotide, and three mononuclear repeat sequences). Microsatellite instability in two to seven loci were found in 15 of 16 (94%) of the patients. This instability is compatible with a mutator phenotype, which predisposes the patients to the development of malignancies including t-leuk.