Acute rheumatism in children in its relation to heart disease.

Date:
1927
Catalogue details

Licence: Public Domain Mark

Credit: Acute rheumatism in children in its relation to heart disease. Source: Wellcome Collection.

    30/114 (page 18)
    members of which it is composed seem to be particularly individualistic. Further difficulties arise owing to the need for discrimination between “‘ group” and “ specific ’’ serological reactions. Bio- chemical analysis has shown that the specific reaction of a virulent: Type I pneumococcus is due to its possession of a “‘ specific soluble substance.” The same is true for Type II, Type III, and —so far as is known—for each fully equipped (7.e., virulent) strain of the heterogeneous Group IV. These “ specific substances,”’ it appears, are chemically different from each other, each being peculiar to its own type, sub-group, or “ individualistic ” strain. The chemists have also shown that, when the “‘ soluble substance ”” has been extracted from a mass of pneumococci, there remains a residue of protein nature which seems to be common to all pneumococci and is responsible for “‘ group ” reactions within the species asa whole. Itseems probable that similar conditions apply to viridans, though this organism has not, as yet, been so fully investigated from the biochemical aspect. The matter will be made clearer by a concrete example of the laboratory questions which actually arise. Rebecca Lancefield!® (1925) investigated very thoroughly four strains of S. viridans which were obtained from blood cultures, two from rheumatic fever patients and two from cases of endo- carditis. By elaborate chemical methods, she separated from each strain a soluble specific substance (8S), which was probably a complex carbohydrate, and a nucleo-protein residue (P). Rabbits were immunised. by intravenous injections of living broth cultures. With the sera thus obtained, it was found that the strains were distinct from each other by ordinary serological tests. Corre- sponding with these distinctions were equally sharp differences. between the S substances ; the S obtained from one strain reacted. with the serum prepared by that strain but not with the sera prepared by the other strains. As regards the P substances she found :—‘ A close relationship between nucleoproteins from different strains of Streptococcus viridans is suggested by the existence of a certain amount of cross-precipitation and a larger degree of cross-complement fixation. But the occurrence of stronger reactions with homologous nucleoproteins than with heterologous indicates that there is some degree of individual difference in proteins from separate strains.”’ She concluded. that “two distinct antibodies are present in the sera for Strep- tococcus viridans ; one of high titer implicated in the parallel pheno- mena of agglutination and. precipitation by the soluble specific substance, the other usually of low titer and involved in precipit- tion by nucleoproteins but probably little, if at all, in agglutination.” But by prolonged immunisation with living bacteria she found it possible to produce sera with a high content of antibodies for Pas wellasforS. She observed that “ the specific antibodies were not reactive with proteins but were active with high dilutions of the soluble specific substance and were responsible for