Bacteriological studies.

  • Great Britain. Ministry of Health.
Date:
1923
Catalogue details

Licence: Public Domain Mark

Credit: Bacteriological studies. Source: Wellcome Collection.

    9/74 (page 3)
    bacterium by neutralising or diverting the attack of the host’s antibacterial forces. This brief mention of some of the conditions which have to be considered at the outset of immunological discussions on infection and resistance may suffice to show that the question of bacterial virulence in relation to human infection cannot be answered. in simple bacteriological terms, because it involves the inter- relationship of complex factors which are not constant. Both the invasive capacity of the bacterium and the host’s power of resistance are subject to variation, and it is often impossible to discriminate between the influence of the one factor and the other upon the incidence of infection and the course which it runs. { think it is important to emphasise these general considerations, because they mean that it is useless to expect the discovery of any one clue which will unravel the whole subject. Owing to its complexity, the problem must be divided into sections and these, in turn, must be subdivided into smaller sec- tions, each of which needs separate consideration. And it must be recognised, as a necessary consequence of this method of inquiry, that conclusions derived from consideration of any particular sub-section are not immediately applicable to the problem as a whole; they relate only to one factor, which must be correlated with many other factors. One large section of immunity work is occupied with the reactions between antigens and antibodies. Highly important though it is, this subject is no more than a part of the whole; even if knowledge about antigens and antibodies were complete, it would be only a partial explanation of infection and resistance. This section, again, lends itself to many sub- divisions, and it is on one of these that I wish to concentrate attention in this report. When bacteria are introduced into the body parenterally, antibodies are formed which are directly attributable to the antigenic stimulus of foreign protein; and these events usually happen whether the bacteria are dead or alive. But is this a complete statement of the antigenic influences which are operative when the bacteria actually grow within the tissues of the living animal body? Under these circumstances, is there an additional factor to consider? Are products formed which act as antigens, though differing from the antigens obtained from dead bacterial protoplasm, and stimulate the formation of antibodies which react specifically with these products of bacterial growth? The possibility of this additional antigenic factor is the subject which i have selected for consideration. Its special importance lies in the fact that bacterial virulence, in the many instances where it is not due to a demonstrable toxin, is urgently in need of explanation. It is rarely possible to attribute it directly to the ordinary well accredited bacterial antigens, which can be demonstrated in the test-tube by antibody reactions. Serological tests for precipitins, agglutinins and absorption of agglutinins enable one to identity a bacterial species and to subdivide a species into races or groups; but it is frequently Ad