Ultrastructural morphometry of human leucocytes in health and disease

Eosinophils in the 1990s: new perspectives on their role in health and disease

Eosinophils are characterized by their unique crystalloid granules that contain four basic proteins--MBP, ECP, EDN and EPO. The cell has many common features with neutrophils but, unlike that cell type, eosinophils utilize VLA-4/VCAM-1 as an adherence pathway and have a number of other receptors not shared by neutrophils. These include recognition units for IgE (distinct from CD23), and receptors for IL-5, IL-3 and RANTES. Following stimulation with a variety of agents, eosinophils preferentially elaborate LTC4 as the major 5-lipoxygenase product of arachidonic acid and produce substantial amounts of PAF. Of particular interest is the ability of eosinophils to synthesize a number of cytokines. Thus eosinophils have marked pro-inflammatory potential. There is now convincing evidence that eosinophilia is T-cell dependent. The Th2-type cell, which selectively secretes IL-5 and IL-4, seems particularly involved. IL-5, IL-3 and GM-CSF are required for eosinophil maturation, and cause activation and prolonged survival of the mature cell. IL-5 is unique in that it promotes terminal differentiation of the committed eosinophil precursor and in vivo in mice appears to be sufficient on its own for eosinophil growth from uncommited stem cells. IL-4 selectively upregulates VCAM-1 expression on endothelial cells thus augmenting VLA-4-dependent eosinophil adhesion. The role of eosinophils in disease is complex but in general their numbers are increased in helminthic parasitic disease and atopic allergy and asthma. Eosinophil products can produce many of the pathological features of asthma, and helminthic larvae coated with immunoglobulin or complement are particularly susceptible to eosinophil-mediated cytotoxicity. Eosinopenia is often related to acute inflammation or stress.

Immune-mediated interactions during macrophage development in non-Hodgkin's lymphoma

As part of an investigation of mononuclear phagocytes in malignant lymphoma, measurement of immune-mediated erythrophagocytosis and rosette formation was carried out on cells grown in suspension culture at the monocyte (Day 0) and macrophage (Day 6) stages; the culture medium contained autologous serum. Cells were derived from 10 patients with untreated non-Hodgkin's lymphoma (NHL) and from 12 normal individuals. The results were subjected to Analysis of Variance and demonstrated a significant difference between the two groups with respect to erythrophagocytosis but not to rosette formation. In the NHL group, the proportion of erythrophagocytic cells showed no significant increase between the monocyte and macrophage stages (0.07 to 0.09), in contrast to the marked increase seen in the normal group (0.09 to 0.24). In a pilot investigation to examine the possible role of factors in the serum, cells derived from the NHL patients were cultured with serum from healthy donors; they showed no significant difference in the immune-mediated functions from those grown in autologous serum. Overall, the results provide further quantitative evidence of defective macrophage maturation in NHL, presumably reflecting the compromise of host defence mechanisms.