Previous studies of the biochemistry and physiology of eosinophils have relied upon cells obtained from patients with eosinophilia (EE). It is unknown whether such cells might have been activated or partially exhausted by the pathological state causing eosinophilia. We examined cell surface charge, membrane transport of deoxyglucose, activation of lyso-somal acid phosphatase, and oxidative metabolism to provide a profile to compare EE with purified normal eosinophils (NE) and normal neutrophils.
Eosinophils or neutrophils were obtained in >95% purity from normal individuals and patients with eosinophilia of diverse etiologies. Cell surface charge was determined by electrophoretic mobility in micromoles per second per volt per centimeter. Normal eosinophils demonstrated a surface charge of 2.46±0.03. Stimulation of the cells by zymosan-activated serum (ZAS) reduced the surface charge to 1.82±0.02. In contrast, the charge of “resting” EE was already reduced (1.89±0.05) and was not altered by ZAS. Resting and stimulated neutrophils had a charge of 1.98±0.01 and 1.69±0.02, respectively.
Uptake of [3H]2-deoxyglucose has been shown to reflect carrier-facilitated hexose transport in granulocytes. Deoxyglucose uptake by resting NE and NE stimulated by ZAS was 2.40±0.40 and 5.44±0.39 (cpm × 10−3/2 × 105 eosinophils), respectively. Resting and stimulated EE demonstrated deoxyglucose uptake of 7.55±0.58 and 15.3±0.6, respectively.
Lysosomal acid phosphatase was determined by an electron microscopic cytochemical technique. In normal eosinophils and neutrophils, lysosomal acid phosphatase in mature cells is held in a latent form. Normal eosinophils demonstrated weakly positive acid phosphatase activity in 7.8±1.2% of the specific granules. Normal eosinophils, stimulated by opsonized staphylococci or the calcium ionophore A23187, develop rapid activation of acid phosphatase in ∼80% of the granules throughout the cells. Resting EE were usually already activated and demonstrated acid phosphatase in 48.6±8.6% of the granules (range, 2-95% granules positive; significant activation was observed in preparations in EE from 11 of 15 patients).
Oxidative metabolism was monitored by measurement of the hexose monophosphate shunt (HMPS) (metabolism of 1-[14C]glucose to 14CO2). Previous studies demonstrated that resting EE have an HMPS activity which is nearly that of stimulated neutrophils, yet EE remain capable of further 7-10-fold increase when stimulated by opsonized zymosan. In contrast, the HMPS of NE (resting and stimulated) was not significantly different from that of neutrophils.
Thus eosinophils obtained from patients with eosinophilia appear significantly activated when compared with normal eosinophils by the criteria of surface charge, activation of lysosomal acid phosphatase, membrane hexose transport, and hexose monophosphate shunt activities.