The products of the human ARG gene and the human ABL gene characterize the 
Abelson family of non-receptor tyrosine protein kinases. Both genes are 
ubiquitously expressed. The interactions of these two similar protein kinases 
are still not well known, although it has been suggested that they could 
cooperate, with redundant actions, to provide intracellular signals in the 
cells. Lymphopenia occurs in mice with homozygous disruption of c-abl, 
indicating that in certain tissues Arg is unable to substitute c-abl functions. 
In B and T lymphoid cell lines at different stages of differentiation, we 
studied, by a reverse transcriptase-competitive polymerase chain reaction and 
Western blotting, Arg and c-abl in order to evaluate whether the expression 
pattern of the two genes could give insight as to why they do not exhibit 
overlapping roles in lymphocytes and whether the product levels of the two genes 
are related to lymphoid differentiation. The data showed that their expression 
is differently modified in lymphoid B cell lines. The highest Arg transcript and 
protein levels are in the mature B cells.