Increased activities of cytosol aminopeptidase and lactate dehydrogenase in serum originate from lymphocytes in necrotizing lymphadenitis.

In three pediatric patients with necrotizing lymphadenitis, cytosol aminopeptidase activity (c-AP; EC 3.4.11.1) in serum was markedly increased to 509, 417, and 191 U/L, respectively (normal range 25-60 U/L). Lactate dehydrogenase (LD; EC 1.1.1.27) was also increased, with LD-3 predominating. The increased concentrations of c-AP and LD presumably originated from the destruction of infected, activated lymphocytes, especially T lymphocytes. Necrotizing lymphadenitis is probably caused by a lymphocytotropic virus.