Expression of adenosine deaminase and purine nucleoside phosphorylase isozymes in lymphohemopoietic precursor cells and normal and neoplastic lymphoid populations

Abstract

Adenosine deaminase (ADA) and purine nucleoside phosphorylase (PNP) isozyme profiles were analyzed in rat lymphoid cell populations at differing developmental stages. Day 12 fetal liver and Day 16 fetal thymocytes, both of which are composed of large, basophilic precursor cells, had a single ADA isozyme whereas newborn thymocytes, young adult thymocytes, and all peripheral lymphocytes contained a primary and two secondary ADA isozymes. In contrast, PNP isozyme profiles were virtually identical in all tissues examined, one primary and one secondary isozyme band. A 5-day organ culture of Day 16 fetal thymus resulted in the expression of the primary and two secondary ADA isozyme bands; this finding indicates that secondary ADA isozyme expression during thymocyte development occurs in the differentiated progeny of Day 16 fetal thymocytes which originally expressed only the primary ADA isozyme band. Thus, T-lymphocyte differentiation in the rat is accompanied by the appearance of secondary ADA isozymes whereas PNP isozymes remain essentially unchanged. Gross virus-induced thymic lymphomas such as fetal liver and fetal thymus expressed only the primary isozyme band. Moreover, the thymic lymphomas and Day 16 fetal thymocytes both displayed identical, unique cell-surface antigenic phenotypes. These results support a thymocyte precursor origin for Gross virus-induced thymic lymphomas in the rat.