The analysis of various methods of thymic non-lymphoid cells (TNLC) culture in vitro was performed. The TNLC obtained in culture of small thymic fragments in Eagle's minimal essential medium with 30% of fetal calf serum have been found to be biologically active as indicated by their ability to enhance proliferative activity and Il-2 production of peripheral blood mononuclear cells derived from ataxia telangiectasia patients.