Characteristics of invasive candidiasis in gamma interferon- and interleukin-4-deficient mice: role of macrophages in host defense against Candida albicans.

Murine models of invasive candidiasis were used to study the in vivo importance of gamma interferon (IFN-gamma) and interleukin-4 (IL-4) in host defense against Candida albicans and to characterize the tissue inflammatory reactions, with special reference to macrophages (Mphi). Knockout (KO) IFN-gamma-deficient (GKO) and IL-4-deficient (IL-4 KO) and C57BL/6 parental mouse strains were challenged intraperitoneally with 10(8) C. albicans blastoconidia. Survival of GKO mice was significantly lower (16.7%) than that of C57BL/6 control (55.5%) and IL-4 KO (61.1%) animals, but was not correlated with the extent of organ colonization. Immunohistological analysis with a panel of myeloid and lymphoid markers revealed multiple renal abscesses, myocarditis, hepatitis, meningoencephalitis, and pneumonia in each strain, with a dominant presence of Mphi. In the absence of IFN-gamma, C. albicans induced striking changes in the phenotype of alveolar Mphi and extensive perivascular lymphoid infiltrates in the lung. Impairment in nitric oxide production by peritoneal Mphi was shown only in GKO mice, and they produced Candida-specific immunoglobulin G (IgG), IgM, IgA, and IgG subclasses in lower titers. Our in vivo studies with KO mice elucidate a critical role for IFN-gamma, but not IL-4, in host defense against C. albicans.

Fc chimeric protein containing the cysteine-rich domain of the murine mannose receptor binds to macrophages from splenic marginal zone and lymph node subcapsular sinus and to germinal centers.

Ligands for the cysteine-rich (CR) domain of the mannose receptor (MR) were detected by incubating murine tissues with a chimeric protein containing CR fused to the Fc region of human IgG1 (CR-Fc). In naive mice, CR-Fc bound to sialoadhesin+, F4/80low/-, macrosialin+ macrophages (M phi) in spleen marginal zone (metallophilic M phi) and lymph node subcapsular sinus. Labeling was also observed in B cell areas of splenic white pulp. Western blotting analysis of spleen and lymph nodes lysates revealed a restricted number of molecules that interacted specifically with CR-Fc. In immunized mice, labeling was upregulated on germinal centers in splenic white pulp and follicular areas of lymph nodes. Kinetic analysis of the pattern of CR-Fc labeling in lymph nodes during a secondary immune response to ovalbumin showed that CR ligand expression migrated towards B cell areas, associated with cells displaying distinctive dendritic morphology, and accumulated in developing germinal centers. These studies suggest that MR+ cells or MR-carbohydrate-containing antigen complexes could be directed towards areas where humoral immune responses take place, through the interaction of the MR CR domain with molecules expressed in specialized macrophage populations and antigen transporting cells.

The human lysozyme promoter directs reporter gene expression to activated myelomonocytic cells in transgenic mice.

The 5' region of the human lysozyme gene from -3500 to +25 was fused to a chloramphenicol acetyltransferase (CAT) reporter gene and three transgenic founder mice were obtained. All three transgenic lines showed the same pattern of CAT enzyme expression in adult mouse tissues that was consistent with the targeting of elicited, activated macrophages in tissues and developing and elicited granulocytes. In normal mice high CAT enzyme activity was found in the spleen, lung, and thymus, tissues rich in phagocytically active cells, but not in many other tissues, such as the gut and muscle, which contain resident macrophages. Cultured resident peritoneal macrophages and cells elicited 18 hr (granulocytes) and 4 days (macrophages) after injection of sterile thioglycollate broth expressed CAT activity. Bacillus Calmette-Guérin infection of transgenic mice resulted in CAT enzyme expression in the liver, which contained macrophage-rich granulomas, whereas the liver of uninfected mice did not have any detectable CAT enzyme activity. Although the Paneth cells of the small intestine in both human and mouse produce lysozyme, the CAT gene, under the control of the human lysozyme promoter, was not expressed in the mouse small intestine. These results indicate that the human lysozyme promoter region may be used to direct expression of genes to activated mouse myeloid cells.

Interleukin 4 regulates induction of sialoadhesin, the macrophage sialic acid-specific receptor.

Sialoadhesin is a nonphagocytic lectin-like receptor found on a restricted population of tissue macrophages in lymphoid and hemopoietic tissues. In bone marrow, it is localized to areas of contact between the resident stromal macrophages and developing granulocytes, which together form myeloblastic clusters. Sialoadhesin is highly specific for sialylated glycoconjugates and may play a role in adhesion and trophic hemopoietic cell interactions, although its function is unknown. Resident peritoneal macrophages do not express high levels of sialoadhesin in vitro unless an inducing element found in normal mouse serum is present. The restricted in vivo location of this marker and its induction by mouse serum prompted us to examine the possible influence of various cytokines on its expression, measured by a sheep erythrocyte rosetting assay. None of the cytokines tested was able to induce sialoadhesin; however, interleukin 4 (IL-4) prevented the induction in the presence of serum. Expression of other macrophage markers was not influenced in parallel, and Western blotting showed that sialoadhesin antigen in cell lysates was selectively reduced by IL-4. Inhibition by IL-4 was dose dependent, could be blocked by antibodies to both IL-4 and the IL-4 receptor, and was overcome by increased serum concentrations. IL-4 is therefore a potent cytokine regulator of the sialic acid-specific receptor implicated in macrophage-hemopoietic cell interactions.

"Doing battle": a metaphorical analysis of diabetes mellitus among Navajo people.

Effective communication with patients and their family members forms the foundation of a therapeutic relationship. This is particularly important when the occupational therapist, other health professionals, and the patient are from different cultural backgrounds. This paper describes one aspect of the findings of a ethnographic study of chronic diabetes among the Navajo people (referred to here as Dine'). It focuses on the dominant metaphorical images that were used by the informants to describe their illness experiences. The data suggest that diabetes can be considered a metaphor for larger social changes in the life-style and traditions (e.g., away from sheepherding as a means of basic subsistence to obtaining urban-centered employment) of native Americans and their effects on the Dine'. Implications of our findings include the importance of metaphorical communication for perceptions of compliance, powerlessness, and patient and therapist satisfaction with the therapeutic relationship.

Evidence that Very Slow Wallerian Degeneration in C57BL/Ola Mice is an Intrinsic Property of the Peripheral Nerve.

We have described a mutant mouse, C57BL/Ola, in which Wallerian degeneration following peripheral nerve transection is very slow. Our previous results suggested that recruited monocytes play a role in rapid Wallerian degeneration. The nature of the mutation in C57BL/Ola mice is not known and we have investigated whether the defect is intrinsic to the nerve or due to a defect in the circulating monocytes. We have made chimaeric mice in which bone marrow from histocompatible mice, with rapidly degenerating nerves and normal monocyte recruitment, was used to reconstitute irradiated C57BL/Ola mice and vice-versa. A substantial degree of donor repopulation of the hosts was confirmed by measures of the levels of glucose-phosphate isomerase alloenzymes in blood and tissue samples from the two different strains. The rate of degeneration of the transected sciatic nerve was found to be host-dependent, providing evidence that the mutation affects cell populations intrinsic to the nerve and not the circulating monocytes. We provide additional evidence that the peripheral nerves of C57BL/Ola mice are different from those of other mice as they degenerate at a slower rate in vitro.