Title: 587 LEUKOCYTOSIS, MONOCYTOSIS AND INCREASED PERIPHERAL BLOOD COLONY STIMULATING ACTIVITY (CSA) IN SICKLE CELL DISEASE
Abstract: The leukocytosis of sickle cell disease has not been well characterized. Monocytes are a source of CSA, a leukopoietin active in the control of granulopoiesis in vitro. We subjected hematologic parameters to statistical analysis and assayed peripheral blood CSA in stable patients free of crisis or serious infection. Two × 105 normal marrow cells were layered over 1 × 106 patient or control feeder leukocytes in agar and colonies of > 50 cells enumerated at 14 days. Patient absolute granulocyte counts and monocyte counts were elevated compared to controls (AGC = 6000 ± 3200/mm3, AMC = 790 ± 640/mm3). Myeloid and erythroid precursors were infrequent (< 1%). There was no association between AGC and Hb or reticulocyte levels (p > 0.1). However, AGC and AMC were highly correlated (r = .5, n = 154, p < 0.001). CSA production by 10 patients was nearly two-fold that of paired controls (95 vs 63 colonies/2 × 105 marrow cells, p < 0.001). Feeder layers from which monocytes were removed by surface adherence lost 88% of their activity. We conclude that leukocytosis in HbSS is not correlated with erythrocyte production or indiscriminant marrow release but is associated with monocytosis and elevated CSA production.