An outline of immunity / by W.W.C. Topley.

  • Topley, W. W. C. (William Whiteman Carlton), 1886-1944.
Date:
1933
Catalogue details

Licence: In copyright

Credit: An outline of immunity / by W.W.C. Topley. Source: Wellcome Collection.

    17/432 (page 5)
    GRADES OF IMMUNITY o 2. Acquired Immunity. (a) Active. (a) Naturally acquired. (ft) Artificially induced. (b) Passive. (a) Naturally acquired (congenital). (ft) Artificially induced. Grades of Immunity. We have noted that the kinds of immunity in which we are most interested are never absolute. To keep our ideas clear and precise it will be well to consider briefly the grades of immunity that may, in fact, be demonstrated, remembering always that they shade into one another by imperceptible degrees. Fig. 1 gives, in diagrammatic form, a rough classification that will be sufficient for our immediate needs. It represents an infection of the invasive type, associated with a bactersemia (an invasion of the blood stream by micro¬ organisms) as well as with local lesions ; but it can easily be modified to meet the case of a toxsemic infection. The width of the black wedge-shaped areas at any level may be taken to represent the chance of death, the degree of bactersemia and the extent of the local lesions in an individual, or the frequency of these phenomena, or of latent infections, in a sample of individuals possessed of approximately the same grade of immunity. Thus, starting with the completely susceptible, we may assume that all, or almost all, individuals infected will develop an acutely fatal bactersemic infection. Local lesions will be infrequent, and minimal when they occur. There will be no latent infections. Passing to our next arbitrary grade—partial immunity of low degree—we find fatal bactersemic infections becoming less common, local lesions more frequent and more pronounced, and a small but increasing number of latent infections. With partial immunity of a medium grade we find bactersemia and death much less frequent, local lesions common and relatively extensive, and latent infections increasing in frequency. With partial immunity of a high grade, death no longer occurs, bactersemia is infrequent and, when it occurs, is slight and transient. Local lesions are becoming much less frequent and, when they occur, much less extensive. Latent infections reach a maximum frequency and then begin to decline. Finally we reach the ideal—perhaps the dream ideal—of complete or solid immunity. The host is entirely impervious to all attacks of the parasite. It will not have escaped attention that the grades of resistance that we have labelled as partial immunity are compatible with severe and often fatal infections, and that many infective diseases in their common clinical form might be regarded as occurring in partially immune persons. This view is almost certainly the right one. The syndromes that normally characterize such diseases as typhoid fever, or lobar pneumonia, are expressions of partial