Different strains of rats develop different clinical forms of adjuvant disease.

Evidence is presented that a single injection of bacterial antigen in oil into a footpad of rats of 5 strains induced different clinical forms of adjuvant disease in the individual rat strains. Rats were injected with 300 micrograms heat-killed Mycobacterium tuberculosis in 50 microliters paraffin. Inflammatory lesions and clinical features were recorded on skeletal charts at frequent intervals after injection; methods of charting and quantifying the features are described. By individually marking the rats and using one or more charts per rat we obtained an objective record of the course of disease in each animal and thus a means of distinguishing clinical features from manifestations of disease severity. Evaluation of these records showed that there was a pattern of joint involvement and associated physical and clinical features specific to each strain and that such strain specificity was reproducible in groups of rats injected over periods up to 3 1/2 years. These results suggest that the clinical form of adjuvant disease developing in each rat in response to the injection of mycobacteria in oil is genetically determined, and that there are additional factors that interact with genetic ones to allow adjuvant disease to develop in a particular rat.