Comparative production of interferon by explanted lymphoreticular tissue and alveolar macrophages from rabbits and humans

Interferon production in rat type II pneumocytes and alveolar macrophages

The time course and magnitude of interferon production induced by influenza virus were determined in type II pneumocytes and alveolar macrophages isolated from rats (Sprague-Dawley). Although the peak of interferon production was approximately 20 h in both alveolar cell types, it was more than three- to fourfold higher in type II cells than in macrophages. Dose-response relationships were noted between the virus multiplicity of induction as well as population numbers of either alveolar cell type and interferon yields. The viral-induced cytokines produced by rat type II cells and alveolar macrophages exhibit physiochemical and biological properties characteristic of interferons and, with respect to type II pneumocytes, mark their heretofore unrecognized capability to produce interferon. The best cross-species antiviral protection afforded by these rat interferons to cells of different origin, expressed as percentage of homologous species (100%), was as follows: guinea pig 50, mouse 40%, and both human and monkey 0%. The heterologous antiviral activity by interferons from either rat alveolar macrophages or type II cells on alpha interferon-sensitive guinea pig cells suggests that these cytokines may be more appreciably related to the alpha-like interferon species. The growth of influenza and Sendai viruses was precluded in both rat alveolar macrophages and type II pneumocytes. The findings herein suggest that type II cells may be a major source of alveolar interferon for activating the antiviral state and modulating alveolar cell functions requisite for lung integrity.

Interferon production by leukocytes infiltrating the lungs of mice during primary influenza virus infection

Lung fluids and leukocytes were obtained from unprimed C3H mice by transpleural lavage at intervals after infection with influenza A/Hong Kong/68 virus and were tested for interferon activity. Lavage fluid interferon titers correlated directly with lung virus titers and with initial increases in leukocyte yields from infected lungs. In contrast to cultured lymph node cells from infected animals or leukocytes from lungs of uninfected mice, washed leukocytes obtained from the lungs of mice infected 2 to 6 days earlier produced interferon spontaneously in culture. The physiochemical, biological, and antigenic properties of both the interferon in lavage fluids and that produced by lung lavage leukocytes were similar and characteristics of alpha interferon. Fractionation studies indicated that macrophages and T lymphocytes were primarily responsible for the interferon produced in culture. The early presence and significant numbers of interferon-producing leukocytes in infected lungs suggests that these cells have an early role in defense against influenza virus infection.

Production of interferon by an SV40-transformed macrophage line, BB-W-531-2

A simian virus 40-transformed mouse macrophage line, BB-W-531-2, was examined for its ability to produce interferon. BB-W-531-2 cells showed a phenotypic change between the macrophage and the nonmacrophage states. A viral inhibitor (interferon) was produced by the cells during the phenotypic change from the nonmacrophage to the macrophage state. Cells having macrophage properties were well capable of producing interferon when they were stimulated with ultraviolet-inactivated vaccinia virus, lipopolysaccharide, a streptococcal preparation (OK-432) or polyinosinate . polycytidylate. In contrast, cells that had lost their macrophage properties did not produce interferon even when they were given the same treatments as the cells having macrophage properties. The results suggest that the ability of BB-W-531-2 cells to produce interferon is associated with the expression of several macrophage properties.

Thermal stability and interaction with ferret inflammatory exudates of two clones of influenza virus of differing virulence for both ferrets and man

After intranasal inoculation of ferrets with influenza virus the upper respiratory tract infection diminishes during the second day and the onset of this reduction occurs earlier for an attenuated clone (64d) than for a virulent clone (7a) of the recombinant virus A/PR/8/34-A/England/939/69 (H₃N₂). The relevance of pyrexia and the nasal inflammatory response to this reduction in infection has been investigated.

Egg-grown Clone 64d was more thermobile than Clone 7a at normal and pyrexial temperatures when suspended in egg allantoic fluid or phosphate-buffered saline. However, in infected nasal washes, both clones were rapidly inactivated when the washes were incubated at these temperatures.

In vitro tests showed that both clones adsorbed to the phagocytes of peritoneal exudates from uninfected ferrets and nasal inflammatory exudates of ferrets infected with both clones. About 90% of the virus was adsorbed after 30 min at 0° or 370° and only 2-14% of this was recovered after treatment with receptor-destroying enzyme followed by freeze-thawing the cells. In contrast, high recoveries (36-112% of that adsorbed) were obtained from red blood cells that were treated similarly. Significant differences were not detected between the clones in either adsorption by or recovery from phagocytes of the different types of exudates.

Thus pyrexia and the nasal inflammatory cells probably play a major role in the reduction of nasal tract infection but, while pyrexia may have had some influence, no evidence was obtained to indicate that the cells contributed to the earlier reduction of Clone 64d.