Alveolar macrophage characteristics: effect of repeated lavages on cell activity

Evaluation of alveolar macrophage function after experimental infection with equine herpesvirus-1 in horses

The role of the pulmonary alveolar macrophages (PAM) in the lung defense mechanism was evaluated in horses infected with equine hespesvirus-1 (EHV-1). Five adult horses were exposed to 10(6.6) TCID50 EHV-1 by intranasal instillation. Cytology of bronchoalveolar lavage (BAL) was performed using cytocentrifugation of samples and slides stained by Rosenfeld. Cell concentration was adjusted to 2<FONT FACE=Symbol>´</FONT>10(6) cells/ml, for the measurement of macrophage activity - spreading, phagocytosis of zymosan particles and release of hydrogen peroxide (H2O2). All animals were positive in virus isolation on the second, third and fifth days post-inoculation (DPI). Seroconversion was observed on the 14th DPI. Lymphocytosis was observed by BAL cytology on the 16th DPI. Measurement of macrophage activity demonstrated a marked increase in the spreading rate, on the 23rd and 30th DPI. Phagocytosis was decreased on the second DPI, and returned to levels similar to those observed before inoculation on the 23rd DPI. The amount of H2O2 released by PAM declined on day 2, but, by day 16, they returned to values similar to those observed before inoculation. The decline in PAM activity in the acute phase of disease is indirect evidence that these cells have an important role in lung defense mechanisms against this agent.

Flow cytometric determination of oxidative burst activity of equine peripheral blood and bronchoalveolar lavage-derived leucocytes

Flow cytometric techniques were developed for the evaluation of oxidative burst activity in equine peripheral blood neutrophils and lymphocytes, as well as bronchoalveolar lavage derived pulmonary alveolar macrophages and lymphocytes. The oxidation of dichlorofluorescin was measured by the increased fluorescence of cells stimulated with phorbol myristate acetate or a variety of other stimulants. Flow cytometry was a suitable method for the evaluation of the intracellular oxidation in all cell populations evaluated. Analysis was rapid and cell separation before analysis was not required. Heterogenous cell populations with differing responsiveness to phorbol myristate acetate stimulated oxidative burst were identified in peripheral blood neutrophil and alveolar macrophage populations. The current study characterizes flow cytometric techniques for the evaluation of oxidative burst activity in equine peripheral blood and bronchoalveolar lavage-derived leucocytes.

The flow cytometric evaluation of phagocytosis by equine peripheral blood neutrophils and pulmonary alveolar macrophages

Flow cytometry was used to assess the phagocytosis of fluorescent-labelled bacteria by equine peripheral blood neutrophils and pulmonary alveolar macrophages. Cell populations were prepared from venous blood following ammonium chloride lysis and from washed bronchoalveolar lavage derived samples. Discrete clusters of cells, corresponding to different leucocyte groups, were readily identified on the basis of differing light scattering properties and could thus be discriminated, negating the need for prior cell separation. Cells able to associate with fluorescent-labelled bacteria (by attachment to the cell membrane or by internalization within the cell) acquired increased fluorescence and were readily differentiated from cells unable to interact with bacteria. The fluorescence of bacteria attached to the cell surface was quenched by the addition of trypan blue or counterstained by the addition of ethidium bromide to the assay, thus permitting identification of cells which were able to internalize bacteria.

Effects of 4-ipomeanol on bovine alveolar macrophage function

The objective of this study was to determine whether 4-ipomeanol toxicosis in calves impairs alveolar macrophage functions important in pulmonary defense against infectious agents. Male Holstein calves were given either 4-ipomeanol (3 mg kg-1, i.v.) or vehicle (polyethylene glycol 400). Alveolar macrophages were recovered by pulmonary lavage 3 days later, and their capacities to phagocytose and kill E. coli, migrate toward zymosan-activated immune bovine serum, and produce interferon and interleukin-1 activity were evaluated in vitro. Alveolar macrophages recovered from 4-ipomeanol-treated calves had over a 70% decrease (p < 0.01) in chemotactic activity and over a 37% decrease (p < 0.005) in their capacity to phagocytose E. coli as compared to macrophages from control calves. Interleukin-1 activity in macrophages from 4-ipomeanol-treated calves tended to be higher than that from control calves, but the differences were not statistically significant (p = 0.06). 4-ipomeanol did not affect macrophage bactericidal activity or production of interferon. These results indicate that 4-ipomeanol suppresses select functions of alveolar macrophages in cattle that may be important in pulmonary defense against bacterial pathogens.

The effects of aging on the function of alveolar macrophages in mice

In order to determine whether the function of alveolar macrophages (AM) is modulated by aging, we measured the TNF-alpha production, phagocytic function, and surface antigen expression of AM from young and old mice. When AM were primed by IFN-gamma (500 units/ml) and triggered by LPS (100 micrograms/ml), TNF-alpha production by AM was significantly smaller in old mice as compared with young mice (young mice: 161.7 +/- 28.2 units/ml; old mice: 89.3 +/- 13.6 units/ml, P < 0.05). The percentage of AM which phagocytosed latex particles (more than one particle) in old mice was significantly lower than in young mice (young: 78.1 +/- 2.5%; old: 62.8 +/- 3.4%, P < 0.05). Ia antigen expression of the AM was significantly higher and asialo-GM1 antigen expression was significantly lower in old mice than in young mice (Ia: young, 0.030 +/- 0.005; old, 0.092 +/- 0.024, P < 0.05; asialo-GM1: young, 0.-9 +/- 0.01; old, 0.75 +/- 0.07, P < 0.01). These results suggest that alveolar macrophage function is at least decreased in part with aging in mice.

Rotavirus particles function as immunological carriers for the delivery of peptides from infectious agents and endogenous proteins

A major problem in the development of useful animal subunit vaccines has been the generation of immune responses to weakly immunogenic molecules. For this purpose a new and effective delivery system has been devised. This system is based upon the inner capsid of bovine rotavirus. Under the appropriate conditions, the inner capsid protein, designated BP6, can be made to self-assemble in vitro and form spherical particles. These particles possess an inherent capacity to target to cells of the immune system. Exploitation of these properties has led to the development of technology to couple antigens to the VP6 particles such that the sphere acts as a novel immunological carrier. This is based on a "binding peptide" derived from another rotavirus peptide, VP4, as well as on more traditional techniques of chemical coupling. We have coupled peptides or proteins to this carrier via the binding peptide and have shown that every epitope tested to date gave excellent immune responses. Furthermore, using this carrier, immunity has been developed without the use of adjuvants. This has far-reaching implications for animal and human immunization.

Ability of mononuclear phagocytes from cattle naturally resistant or susceptible to brucellosis to control in vitro intracellular survival of Brucella abortus

The role of bovine mammary macrophages and peripheral blood monocyte-derived macrophages in natural resistance to bovine brucellosis was evaluated. A group of 11 naturally resistant and 10 chronically infected susceptible cows was studied following challenge with Brucella abortus. Macrophages from a greater proportion (P less than 0.026) of naturally resistant cows were significantly superior to macrophages from susceptible cows in their ability to inhibit the in vitro intracellular replication of B. abortus after challenge exposure. Studies of a second group of cows used mammary macrophages from 12 heifers and blood monocyte-derived macrophages from 22 bulls and heifers. These tests were completed before exposure to B. abortus, using mammary macrophages (P less than 0.039) and blood monocyte-derived macrophages (P less than 0.045), and also showed that macrophages from naturally resistant cattle were significantly superior in their ability to control the in vitro intracellular replication of B. abortus. Our data indicate that the mononuclear phagocytes from more than 80% of the resistant cattle controlled intracellular replication of B. abortus significantly better than did mononuclear phagocytes from susceptible cattle. Mononuclear phagocyte function appears to be an important factor in determining natural resistance to bovine brucellosis.

Effect of strenuous exercise stress on chemiluminescence response of equine alveolar macrophages

Bronchoalveolar lavage samples were collected using a fibreoptic endoscope from horses at specified times before and after single bouts of exercise. Lucigenin-dependent phagocytic chemiluminescence was used to assess the effect of exercise on the alveolar macrophage metabolic activity in response to stimulation by opsonised zymosan. A profound suppressive effect on the chemiluminescence production was present throughout the first three days after exercise. However, the cellular composition of lavage fluids was not altered by the exercise. It is suggested that strenuous exercise may jeopardize the antimicrobial function of alveolar macrophages which may lead to an increase in susceptibility to infection.

Bronchoalveolar lavage cytology in cynomolgus monkeys and identification of cytologic alterations following sequential saline lavage

Total and differential cell counts were determined on cytolytic specimens obtained by fiberoptic bronchoscopy and bronchoalveolar lavage (BAL) of five normal cynomolgus monkeys. Total nucleated cell counts ranged from 100 to 430 cells/microliters. Macrophages were approximately 91% of total nucleated cells, while lymphocytes were 3%, neutrophils 4%, and eosinophils 2% of the initial BAL from each monkey. Less than 1% of the cells were mast cells and ciliated or nonciliated epithelial cells. The effects of repeated saline BAL on pulmonary cell populations were evaluated. Saline lavage of individual lung lobes resulted in a marked rise in circulating blood neutrophils at 4 hr after BAL; there was a similar rise in neutrophils in lavage fluids 24 hr after the initial lavage. Differential and total cell counts of both blood and lavage fluid returned to normal if subsequent lavages were spaced at 48-hr intervals. Lymphocytes were not present in saline-lavaged lung lobes, and protein levels of lavage fluids did not rise significantly. BAL produced a transient, reversible, intra-alveolar influx of neutrophils which was preceded by mobilization of bone marrow-stored neutrophils. Neutrophilia in the lavage fluid and blood was not detectable if lavage and blood sampling procedures were done at 48-hr intervals (which did not alter Ia antigen expression among BAL cells). These observations indicate that BAL is a valid method for sampling and assessing pulmonary cellular and fluid constituents if the procedures are done at intervals of at least 48 hr.