'Non-specific' mediators in host defense against respiratory viruses: assay methods and results

Understandably, there is interest in further defining the nature of 'non-specific' defenses. This, in fact, would clarify the specific nature of their appearance and action, as well as their role in host defense. Therefore, 'non-specific' defenses in my discussion will be taken to mean non-immune defenses in virus infections. Tissue or respiratory tract organ cultures are convenient means of studying host defenses in the absence of immune responses. Factors to be controlled in making observations with such systems will be discussed which help 'in vitro' results to parallel 'in vivo' findings. 'In vitro' and 'in vivo' methods and results probing importance of mucous barrier, ciliary activity, temperature and pH will be reviewed. Critical points in separating cellular and humoral immune functions from non-specific mediators will also be touched on. This distinction is complicated by the fact that both limbs of immunity work in close concert with macrophages, PMN's complement and other inflammatory responses. Interferon and macrophage mobilization are examples of 'non-specific' responses which have more recently become complicated by their recognition as part of the effector limb of the cell-mediated immune responses. Finally, methods will also be presented for distinguishing human interferon of the immune-specific variety associated with cell-mediated immunity from that produced by viral infection of non-immune cells.