Because of the widespread dispersion of mononuclear phagocytes throughout the body, there is little quantitative information on their total mass, relative numbers in different sites, or mobilization and redistribution in normal individuals or disease states. It is difficult to obtain such information by direct isolation of macrophages (M401 from all sites where they are known to occur and from tissues in which they are deeply embedded. The pool size of M4~ and their precursors in different compartments has been estimated by van Furth and his colleagues (1) by single-cell analysis after [SH]thymidine labeling, but this method favors enumeration of cells that turn over relatively rapidly, rather than more quiescent resident cells. In principle, antibodies that are specific for M4~ could be used to quantitate the content of antigen (Ag) in tissues directly, without cell separation. F4/80, a rat monoclonal antibody (Ab) directed against a plasma membrane glycoprotein of apparent Mr 160,000, is a specific and sensitive marker for mature mouse Mq~ after isolation (2) and in situ (3). In this study we have assayed F4/80 Ag content in various tissues of normal adult mice by adapting an absorption immunoassay developed by Williams and his colleagues (4) to measure lymphoid differentiation Ag in tissue lysates. We estimated M4~ number by calibrating F4/80 Ag content in a murine M4~ tumor-derived cell line, J774.2. Our results are in good agreement with immunohistochemical findings, and establish that relatively large amounts of F4/80 Ag are found not only in hemopoietic and lymphoid tissues, but also in other sites such as the gastrointestinal tract and normal kidney. This experimental approach provides a basis for further studies on the response of the mononuclear phagocyte system to inflammation and infection. Materials and MethodsAnimals. Tissues, organs, and peritoneal cells were obtained from 8-10-wk-old male mice of the C57BL/6 strain weighing 23 _ 2 g. Swiss mice, Pathology Oxford (PO), were used to prepare M~ target cells for binding assays. This work was supported in part by the Wellcome Trust and the Medical Research Council, UK. Address correspondence and reprint requests to S. Gordon. Preparation of M$ Target Cells. PO mice aged 8-10 wk were injected with 1.0 ml of thioglycollate broth intraperitoneally and peritoneal cells (TPC) harvested 4-6 d later. Cells were cultivated at 37°C in 5% CO~ in Dulbecco's modified Eagle's medium (DME) with 10% fetal calf serum (FCS) in 96-well plates (Sterilin Ltd., Middlesex, United Kingdom [UK]), at a density of 1 x 105 M4~ per well, for 2 d. They were then washed free of nonadherent cells, fixed with 0.125% vol/vol glutaraldehyde, and excess glutaraldehyde removed by washing and further incubation with 10% FCS in phosphatebuffered saline (PBS). Plates were stored in PBS with 10 mM sodium azide at 4°C for up to 12 wk. Preparation of Tissue and Cell Extracts.Organs: Animals were freshly killed by ether and organs removed into ice-cold extraction buffer (PBS containing 3 mM io...

Introduction Morphological assessment of the blood smear has been performed by conventional manual microscopy for many decades. Recently, rapid progress in digital imaging and information technology has led to the development of automated methods of digital morphological analysis of blood smears. Methods A panel of experts in laboratory hematology reviewed the literature on the use of digital imaging and other strategies for the morphological analysis of blood smears. The strengths and weaknesses of digital imaging were determined, and recommendations on improvement were proposed. Results By preclassifying cells using artificial intelligence algorithms, digital image analysis automates the blood smear review process and enables faster slide reviews. Digital image analyzers also allow remote networked laboratories to transfer images rapidly to a central laboratory for review, and facilitate a variety of essential work functions in laboratory hematology such as consultations, digital image archival, libraries, quality assurance, competency assessment, education, and training. Different instruments from several manufacturers are available, but there is a lack of standardization of staining methods, optical magnifications, color and display characteristics, hardware, software, and file formats. Conclusion In order to realize the full potential of Digital Morphology Hematology Analyzers, pre‐analytic, analytic, and postanalytic parameters should be standardized. Manufacturers of new instruments should focus on improving the accuracy of cell preclassifications, and the automated recognition and classification of pathological cell types. Cutoffs for grading morphological abnormalities should depend on clinical significance. With all current devices, a skilled morphologist remains essential for cell reclassification and diagnostic interpretation of the blood smear.

Since the early work of Taliaferro and Mulligan (1), it has been apparent that macrophages (M40 j are prominent in malaria infection, but little is known about the properties of M4~ in malaria and of their precise role in the host response. The outcome of plasmodial infection in the intact host depends on the parasite strain and variation, the animal species, and innate and acquired immune resistance mechanisms that are poorly understood (2, 3). Parasitized red blood cells (PRBC) are cleared by the liver and spleen during malaria infection (4, 5). Studies in vitro have shown increased ingestion of opsonized red cells by splenic Mq~ (6) and killing of parasites by lymphokine-activated monocytes from uninfected individuals via an oxidative burst (7). In murine models, immunity is T cell dependent (8, 9), involving both antibody (Ab) and cell-mediated mechanisms (2, 10). Murine malarias have thus provided a unique means of studying the immune response to malaria both in vivo and in vitro (2, 4-6, 8-10).We have used a strain of Plasmodium yoelii that gives rise to a blood-stage infection characterized by a single wave of parasitemia, self-cure, and acquired immunity, to examine the properties of M4) from control and infected animals. Antigenic, endocytic, and secretory activities have been characterized on M¢~ in liver and spleen and after isolation by collagenase digestion and adherence. We show that the host responds to circulating, parasitized erythrocytes by a dramatic accumulation of M4~ in the blood, liver, and spleen. Circulating monocytes and tissue M4~ from these organs display marked changes in surface and secretory phenotype, compatible with an important role in recovery from infection.

Background: In transfusion-dependent anaemias, while absolute serum ferritin levels broadly correlate with liver iron concentration (LIC), relationships between trends in these variables are unclear. These relationships are important because serum ferritin changes are often used to adjust or switch chelation regimens when liver magnetic resonance imaging (MRI) is unavailable. Objectives and methods: This post hoc analysis of the EPIC study compared serum ferritin and LIC in 317 patients with transfusiondependent thalassaemia before and after 1 yr of deferasirox. Results: Serum ferritin responses (decreases) occurred in 73% of patients, 80% of whom also have decreased LIC. However, 52% of patients without a serum ferritin response did decrease LIC and by >1 mg Fe/g dw (median 3.9) in 77% of cases. Absolute serum ferritin and LIC values correlated significantly only when serum ferritin was <4000 ng/mL (r = 0.59; P < 0.0001) and not at higher levels (≥4000 ng/mL; r = 0.19). Serum ferritin response was accompanied by decreased LIC in 89% and 70% of cases when serum ferritin was <4000 or ≥4000 ng/mL, respectively. Conclusions: As serum ferritin nonÀresponse was associated with LIC decrease in over half of patients, use of liver MRI may be particularly useful for differentiating true from apparent non-responders to deferasirox based on serum ferritin trends alone.