CLONING EFFICIENCY AND SPONTANEOUS MUTANT FREQUENCY IN CIRCULATING T-LYMPHOCYTES IN ATAXIA-TELANGIECTASIA PATIENTS

The mutant frequency at the hprt locus in circulating T-lymphocytes has been determined in 16 ataxia-telangiectasia (A-T) patients, 19 A-T heterozygotes and 12 A-T sibs. Mutant frequency in the A-T patients is highly significantly elevated as a group, even when the relatively poor cloning efficiency of many of the A-T lymphocyte samples is taken into account. However, within the A-T set, considerable variation in both cloning efficiency and mutant frequency is seen. Cellular radiation sensitivity, measured by clonal survival assays and chromosome breakage, also varies, as do the clinical symptoms of the patients, including the age st which they become wheelchair bound and the severity of their telangiectasia. Here all the information available to us on this group of patients is presented in an attempt to discern if there is any relationship between those cellular characteristics we have observed and the severity of the symptoms and progression of the disease in the patients. Although we feel that it may be relevant that the adult patients in our study all have mutant frequencies that are not highly elevated, insufficient data are available at present to resolve any relationship between the heterogeneous clinical symptoms and cellular responses seen in the A-T patients as a group.