A diffusable clastogenic factor in ataxia telangiectasia.

Cocultivation of plasma and lymphocytes from ataxia telangiectasia (AT) patients with those of normal individuals resulted in a significant increase in chromosomal damage in the normal cells. Tissue culture medium used to cultivate AT skin fibroblasts also significantly increased chromosome breakage in PHA-stimulated normal lymphocytes. This clastogenic effect was maximal when the "conditioned medium" was 8-9 days old. A similar effect was not observed with medium derived from normal skin fibroblasts. These observations suggest the presence of a clastogenic factor in the plasma of AT patients which may also be produced by AT skin fibroblasts in culture.