Circulating deoxyribonucleic acid-synthesizing mononuclear leukocytes. I. Increased numbers of proliferating mononuclear leukocytes in inflammatory disease

To quantitate deoxyribonucleic acid (DNA) synthesis by circulating human blood mononuclear leukocytes, buffy coat suspensions were incubated with tritiated thymidine in vitro, and incorporation was measured by liquid-scintillation counting. Elevated mononuclear leukocyte DNA synthesis was found in a wide spectrum of inflammatory diseases, including 2 patients with agammaglobulinemia and infection. Increased thymidine uptake was found especially in the acute phase of disease and tended to decrease with, clinical improvement of the patient. Uptake was lower in patients with chronic inflammatory diseases. No correlation was found between the mononuclear leukocyte thymidine uptake and the erythrocyte sedimentation rate or the total mononuclear cell count. Autoradiographic studies revealed that the tritium-labeled leukocytes had the appearance of atypical lymphocytes and did not phagocytize latex particles. Similar labeled mononuclear cells were found in the blood of a patient with Swiss-type agammaglobulinemia and pneumonia. It was suggested from the data obtained that proliferating cells may appear in the blood in response to inflammation. Some may represent lymphoid cells which participate in an immune response associated with the disease process involved, and some may be precursors of monocytes released in response to acute tissue injury.