The enzymatic specific activity of ADA (which takes into account the reduced tissue weights of wasted mice) is increased in the spleen and cerebellum but decreased in the thymus of these mutants (J:12932). Wasted mutant mice have marked lymphoid hypoplasia in the spleen, thymus, lymph nodes, and peripheral blood. Wasted mice show some similarities to human ataxia telangiectasia (AT; MIM 208900; human gene, ATM; mouse gene, Atm) (J:6766), but there are also numerous differences. But the mutant mice lack the increased sensitivity of spleen cells to killing by ultraviolet radiation (J:20567), the increased sensitivity of cultured fibroblasts to killing by X or gamma radiation (J:8348, J:13960), and the increased post-irradiation inhibition of DNA synthesis (J:7561) characteristic of AT. In addition, the immunological defects of wasted mice differ considerably from those in human AT (J:8288). Wasted mice have a severely reduced number of IgA plasma cells in the entire large and small intestine, but the level of such cells in spleen and the level of serum IgA are normal (J:7903). The mutants also show an extensive cytokine imbalance of many immunologically relevant gene products (IL5, IL1, IL2, IFNG, and TGFB1) which may trigger the wasted pathogenesis (J:19431). The overlapping similarities between AT and wasted, however, have suggested the possibility that Eef1a2 and Atm may be involved in a common pathway, such as a signal-transduction pathway that regulates protein synthesis (J:48050). In fact Eef1a2ws mice show abnormal expression of the proliferating cellular nuclear antigen (PCNA) in the thymus (J:37955).