P94(FER) FACILITATES CELLULAR-RECOVERY OF GAMMA-IRRADIATED PRE-T CELLS

p94(fer) is a ubiquitous, nuclear and cytoplasmic tyrosine kinase, who se accumulation has been demonstrated in all mammalian cell Lines anal ysed. In the present work, the p94(fer) expression profile was determi ned in cell lines which were not tested before. While being present in several hematopoietic and non hematopoietic cell lines including thym ic stromal cells, the p94(fer) kinase could not be detected in pre-T a nd T cell lines. p94(fer) was also absent in pre-B line, but accumulat ed in these cells upon their induced development to antibody producing cells. This is in agreement with the absence of p94(fer) in primary t h,mic and splenic T lymphocytes and its induced accumulation in stimul ated B cells. Relatively high p94(fer) levels were detected in primary thymic and splenic stromal cells. Ectopic expression of p94(fer) in p re-T cells slightly affected their cell cycle profile but it did not a ffect their apoptotic death which was induced by ionizing radiation. H owever, p94(fer) facilitated dramatically, the cellular recovery of ga mma irradiated pre-T cells which have escaped the apoptotic death. The enhanced recovery of the irradiated, p94(fer) expressing pre-T cells, resulted most probably from their increased survival, rather than fro m a prominent change in their proliferation rate. The absence of p94(f er) from pre-B and pre-T cells, may thus contribute to the relative se nsitivity of these cells to ionizing radiation and to their dependence on the functioning of other nuclear tyrosine kinasese.